Zenainder wrote:1. Do I choose one over the other based upon my temperment?
vipassana and samatha meditation go hand in hand. If you struggle to observe a given phenomenon you may start practicing some more samatha to gain stronger samadhi in order to be focused properly.
Zenainder wrote:2. Based upon my practice now, assuming my understanding is accurate, I fall into the samatha practice (observing breath at nostrils; tranquility). Are both or only one of these a path to jhanas?
samatha practice leads to jhana, vipassana practice leads to wisdom
Zenainder wrote:I ask as I have a specific, unexplainable, interests in the jhanas. If I need to be guided in the other direction, please do as I am leaving myself open.
It is important to balance samatha and vipassana practice. Even the highest level of samadhi or jhana will not lead to liberation. On the other hand vipassana with weak samadhi degenerates to mere thinking and does not lead to insight and wisdom.
Zenainder wrote:In the end, as I understand it, both practices have the ultimate goal of nibbana.
The ultimate goal nibbana can only be reached by practicing the N8P. In short this is sila, samadhi and pañña. Samatha and vipassana practice can be summed up to samadhi and pañña but without sila samadhi is weak and with weak samadhi vipassana cannot penetrate to the truths.
best wishes, acinteyyo