I don't want to sound soft or anything, but at age 26 and having gone through a few relationships whether you can hold a long conversation with her is more important than any physical feature. There is only so many times a day you can have sex and believe me, she doesn't want it as much as you do because her sex organs are not dedicated to solely producing the "horny" hormone of testosterone. Henceforth, you better find common ground in conversation or she just might as well be your booty call.
Honestly, I notice the hips first, which translates into buttocks second. Coincidentally, all of my girlfriends have been in the 5'1" to 5'5" range (I am 6'0" myself). Women in this range tend to have curvy hips with a nice ass and a decent rack to boot.
