Penis shapes are what make tham all unique and beautiful, so I can't really say I prefer one type over another, I just want to SEE them! Curves give cocks a lot of character, so visually that's a good thing, but a straight out "rocket cock" is great too. When they are rock hard, they look very excited and throbbing, and that makes me hot, but when they are a little flexible, it make for very good head, so either way. As long as it gets hard enough for penetration, I'm happy. Also, some guys have varying degrees of erections, both in size and firmness, and this is a real turn-on because it's like having several different penises all in one.
Excuse me, I have to go now....