This old cat's attempt at answering this: (and no I am not an expert on anything except fumbling around life)
Firstly, the ideals of a Bodhisatta as defined by the Theravada and the ideals of a Bodhisattva in the Mahayana are different.
In the Mahayana, a Bodhisattva can range from one who has just started on the Path to realized Buddhas who manifest in the Sambhogakaya (Reward body) to actuate their vows made when They first started out on the causal ground for the sake of the deliverance and leading sentient beings to the Dharma. Examples like Avalokitesvara, Manjusri, Vajrapani and so forth are such to exemplify that point. Even Sakyamuni Buddha, has this to say in the Lotus Sutra:
"The Thus Come One's power of spiritual penetrations is acknowledged by all gods, humans, and asuras in the world.
They say that Shakyamuni Buddha, having left the palace of the Shakyan clan and having gone to a place not far from the city of Gaya to sit in the Bodhimanda, has now attained anuttarasamyaksambodhi.
"However, good men, I actually realized Buddhahood limitless, boundless, hundreds of thousands of myriads of kotis of nayutas of eons ago.
"From that time on, I have always remained in the Saha World, speaking the Dharma to teach and transform beings.
Also, in other places, in hundreds of thousands of myriads of kotis of nayutas of asamkhyeyas of lands, I have guided and benefited living beings.
"Good men, in that interval, I spoke of the Buddha Dipankara and others, and I further spoke of them as entering Nirvana, but those were just discriminations made expediently.
"Good men, if a living being comes before me, I observe with my Buddha eye his faith and other qualities, as well as the keenness or dullness of his faculties, and I take him across in an appropriate manner.
"In all places, although the names by which I refer to myself are different and I may be older or younger, I also appear and announce that I am about to enter Nirvana. I also employ various expedient devices, speaking the subtle and wonderful Dharma and enabling living beings to bring forth happiness in their minds.
"Good men, the Thus Come One, seeing living beings delighting in lesser dharmas, beings of scanty virtue and heavy defilements, speaks for these people, saying, 'When young, I left the home-life and attained anuttarasamyaksambodhi.'
In truth, however, I became a Buddha a long time before that. I speak in this way merely as an expedient to teach and transform living beings and to cause them to enter the Buddha Way."
"Thus since I realized Buddhahood in the very remote past, my life span has been limitless asamkhyeyas of eons, eternal and never extinguished.
Good men, the life span I realized when formerly practicing the Bodhisattva path has not yet been exhausted and is twice that of the above number.
In a summarised verse:
From the time I attained Buddhahood,
The eons that have passed
Are limitless hundreds of thousands of myriads
Of kotis of asamkhyeyas in number.
I always speak the Dharma to teach and transform
Countless millions of living beings,
So they enter the Buddha Way.
And throughout these limitless eons,
In order to save living beings,
I expediently manifest Nirvana.
But in truth I do not pass into quiescence.
I remain here, always speaking the Dharma.
I always stay right here...
I speak various Dharmas for their sakes
To save them in an appropriate manner.
I am always thinking,
"How can I cause living beings
To enter the Unsurpassed Way
And to quickly perfect the body of a Buddha?"
Secondly, the 4 stages of Sainthood are also found in the Mahayana, only that more is added to that discipline. So let's concede that this is where the 2 Paths will differ. I will share with you what some of my conversations with certain Monastics and learned laity have yielded:
1. It is not true that one can 'delay' Nirvana. One meaning is that what is construed as the 'attainment of Nirvana' in one school may not be so in the other but merely a high level of attainment for the latter. For one example of what the attainment of Nirvana is to Mahayanists, read it in the Lankavatara Sutra's CHAPTER TWO: COLLECTION OF ALL THE DHARMAS: XXXVIII. On Nirvana
And a simple link on what constitutes an Arhat: http://www.drba.org/dharma/btts/9xxentr ... .asp?wid=9
2. From the very beginning, based on point 1, on the causal ground, the Mahayana Path is to be practiced with this in mind: for the benefit of all sentient beings and this is known as the Bodhicitta in its most simplistic term. Now that does not mean that one neglects oneself in that pursuit but rather 'for all sentient beings' includes oneself in that 'benefiting for all'. So one still has to practice the perfections as taught in the 4 Stages of Sainthood and more. After all, how can a mere rookie hope to deliver others when him/herself is not free of that very bond?
3. So, on another level, in the Mahayana when one speaks of 'attainment' and 'non-attainment', it is spoken with a non-duality concept and coupled with the understanding of Sunyata (another subject by itself). So read on one view of what the Mahayana regards as non-duality:The Dharma-Door of Nonduality
and also this excerpt:
...most cultivators are still attached to "duality," and have not reconciled essence and marks, existence and non-existence, noumenon and phenomena.
That is why they embrace essence to reject marks, noumenon to reject phenomena, Emptiness to reject Existence, and vice versa -- thus creating disputes, doubts and perplexity.
Little do they suspect that there is mutual identity between noumenon and phenomena -- phenomena are noumenon, noumenon is phenomena.
If we divide them and consider them separately, phenomena are not true phenomena, noumenon is not true noumenon. This is true also of essence and marks, existence and non-existence and other dualistic dharmas.
For this reason, the Vimalakirti Sutra speaks of the non-dual method to destroy this attachment.
Non-dual means reconciling all things, penetrating into their very nature; it does not mean "one." This is the true realm of "Mind-Only."
Any other doctrine based on the Dharma Doors of Existence or Emptiness is merely an expedient for teaching purposes.
The Theravada POV on Dhamma and Non-duality
Thirdly, one illustration used in a talk I once attended:
From the Mahayana POV:The chilli sauce bottle:
At this stage, sauce and smell are eliminated and finally even the bottle is gone. This is where the level of a Samyak Sambuddha is 'attained'. The smell of chilli sauce:
At this stage, when the 'sauce is gone', the Bodhisattva goes through the 'higher practices' like the Ten Grounds of Bodhisattvahood (see simple link here: http://www.drba.org/dharma/btts/9xxentr ... sp?wid=221
) and also this short summary:
http://www.purifymind.com/glossaryT.htmTen Stages of Bodhisattva
These are the ten stages of development of Bodhisattva depending on their merits and virtues:
1.Pramudita (joy) - job at having overcome the difficulties and sufferings, now entering on the path to Buddhahood
2.Vimala (purity) - freedom from all possible defilement
3.Prabhakari (enlightenment) - stage of further enlightenment
4.Arcismati (wisdom) - stage of glowing wisdom
5.Sudurjaya (no difficulty) - stage of mastering the utmost difficulties
6.Abhimukhi (open way) - the open way of wisdom above definitions of impurity and purity
7.Duramgama (proceeding afar) - getting above ideas of self in order to save others
8.Acala (unperturbed) - attainment of being unperturbed
9.Sadhumati (discriminatory wisdom) - the finest discriminatory wisdom, knowing where and how to save, and possessing the Ten Powers
10.Dharma megha (law cloud) - attainment of the fertilizing powers of law cloud
to get rid of the fine traces of Samsara and Delusion that are still at the 4th Stage of Sainthood. The chilli sauce:
At this stage, on the causal ground, a Bodhisattva learns to transcend this, i.e via the 4 Stages of Sainthood.
Now there are some Mahayana schools that combines both of the first two: 'chilli sauce and its smell' as one stage of training. So, it's as if they are saying that one does not have to go through the 4 Stages but straightaway, start off on the stages of Bodhisattvahood. But again, that's another topic by itself.
In summary see this sample commentary on Ksitigarbha Bodhisattva by the late Ven Master Hsuan Hua:
http://www.buddhistdoor.com/OldWeb/bdoo ... sutra1.htm
Long ago in the distant past Earth Store Bodhisattva vowed,
"If the hells are not empty I will not become a Buddha; only when living beings have all been saved, then I will attain Bodhi."
The hells cannot cease to exist until the karma and the afflictions of living beings have come to an end, and that can never happen because of the nature of living beings.
In the view of everyday science and philosophy, isn't Earth Store Bodhisattva's behavior irrational?
Doesn't it mean that Earth Store Bodhisattva will never have the opportunity to become a Buddha?
No, it does not mean that he cannot become a Buddha, and his vow is by no means irrational. His behavior is in fact a manifestation of great compassion.
Since he made the vow, "Only when all the hells are emptied will I become a Buddha; only when living beings have all been saved will I attain to Bodhi,"
Earth Store has used his awesome spirit to subdue living beings who have accumulated bad karma.
He thus has passed through an un-thinkably long time yet still has not realized Buddhahood, because after one being has been taken across, there is yet another ready to go, and after that one, still another.
There is no one-to-one correlation between the number of beings born and those entering nirvana, since those who are born outnumber those who attain nirvana by tens of hundred of millions.
The same relationship exists in the realm of birth and death; the number of births in any given period is greater than the deaths in the same time.
Those who are to die have to grow old and pass through an entire life before that happens, but those who are waiting to be born only have to spend nine months in the womb.
Since birth is such a rapid process, the persons born greatly outnumber the dying at any given moment.
For this reason Earth Store Bodhisattva has not yet become a Buddha.
He does not, however have any regrets about his vow, and the more living beings there are to rescue, the more he has to do.
And the Ven Master continues here...
"Hear me now in the palace of the Trayastrimsa Heaven as I praise Earth Store Bodhisattva's beneficial and inconceivable deeds among men and gods, his rapid progress in the causes of wisdom, his certification on the Tenth Ground, and his ultimate irreversibility from Anuttarasamyaksambodhi."
In the above passage of text the Buddha praised Earth Store Bodhisattva's irreversibility from Anuttarasamyaksambodhi, the Utmost, Right, and Equal Enlightenment.
Although Earth Store Bodhisattva has not yet become a Buddha, the degree of his enlightenment is equal to that of the Buddhas.
There are varying degrees of enlightenment.
Those of the Two Vehicles- Sound-Hearers and those enlightened to causation-are surpassed by the enlightenment of the Bodhisattvas.
The enlightenment of the Bodhisattvas is said to be right and equal, since it can be said to be equal to that of the Buddhas.
Such enlightenment, however, is still not the highest degree, since it is surpassed by that of the Buddha.
Thus only Buddhas are said to have the Unsurpassed, Right, and Equal Enlightenment.
The term "irreversibility" refers to the Three Types of Non-retreat.
The first of these is Irreversibility of Position, so called because there is no retreat to the practices of the Two Vehicles.
The second is Irreversibility of Practice: there is no retreat to the non-cultivating behavior of common people.
The third is Irreversibility of Thought, so called because the thought is firmly fixed on the practice of the Great-Vehicle Dharmas.
I found this nice quote:
http://www.lioncity.net/buddhism/index. ... &p=1113435
For someone on the path for arhatship, mahayana is not necesarilly better, and vice versa.
We practice as best we can in order to develop wisdom and compassion. That's the case in all Buddhist traditions.
So, in short, neither is better, neither is worse, they are merely different courses for different horses.