Concerning the question in the subject:
Not trying to be rude at all, so please don't take offense, but there is no way that question can be answered by someone else for you. It all depends on how you duel. I know I personally love to spin my saber, so I need a good choke point. I use one-handed swings, as well as two-handed, so I need a saber light enough to be able to control with one hand, but long enough for me to grab it with two hands. Also, I enjoy using reverse grip, so based on all of those, I would recommend the Raven as the best saber for dueling.
However, I strongly suggest the Prophecy based on it being a very practical saber, as well as generally positive feedback from the forum (high points being its smaller size. weight, and good choke for spinning).
Concerning your question about the 36 in blade, that is also a tough one to answer. Each saber has a different depth for the blade socket, so there is not standard (one saber may have a 5 inch depth, while another may have a 2 inch depth, leaving a difference of 3 inches (yay math!
)).
So again, I really do not mean to be rude, and I am sorry if that is how my response comes across, but I have seen many threads like this, as well as asked this question myself. My suggestion is to look in the reviews section for a saber that interest you and see what people have to say. I hope you find a saber that fits you perfectly!