Do you mean what type of setting would be most comfortable for square stones, or do you mean which would be more comfortable, asscher or princess cuts? I don't think the diamond shape will make much difference as long as the setting is comfortable.
I agree with Rubybeth re: which cut of stone will be more comfortable....as for which style, I think you need to go try some on, recognizing that when you first put any new ring on, it's going to feel strange. I wear my shared prong eternity on my right hand on a daily basis and I tried to put it on my left hand recently (which is a bit smaller) and it was totally strange feeling. However, by the end of the day, I had gotten used to it. My point is that I think you'll get used to almost anything, so I think that the most important factors are which style appeals to you the most and how secure that style is given your lifestyle.