well as David notes, there was more going on at the second council that wanting to add to the vinaya, there was (to put it in one way) a wanting to loose rules also, I think the names of the groups also give a clue as to who was keeping the original set of rules, although that isn't a guarantee.David N. Snyder wrote:In most situations I would agree with that. However, 227 precepts are a lot of things to follow! And there are bound to be some, as we see even today, who want to relax some of those rules/precepts. And according to the accounts of the Second Buddhist council it was over 10 major points, including using money, eating after midday, etc., i.e., that some wanted to reduce the number of rules, not to add any. If the account we have for the Second Buddhist council is correct, I would say that gives more evidence that the Pali Canon is the earliest Buddhavacana that we know of.Huseng wrote: It was the Sthaviravādins (ancestors of Theravada), not the Mahāsāṃghikas, who wanted to add material to the Vinaya, which led to the schism as the story goes.
Comparative analysis has lead some scholars to believe the Mahāsāṃghika material best represents the earliest available versions of Buddhist texts. They tend to have less material than from other schools, which in the context of religious literature usually means it is the earlier edition because material is usually added, not deleted, over time.
I agree with David in that the Pali canon is the oldest complete canon available to us, as a general rule, the other existing texts may in some cases represent an older version, and it would be up to the individual or group to decide whether or not any noticeable differences add what is not dhamma, or add to better understanding of the dhamma.