Totally depends on the woman. If its her butt that grabs my desires, then butt. If her tits drive me crazy, then tits. I just can't generalize like that.
I love breasts...yes big breasts most of all, but all breasts are great. I wish I could just rest my head on a nice soft pair of breasts all night long.
Maybe part of the reason I feel as I do is because, weird as it is, I have a butt (and legs) which many men would consider magnificent on a woman. So it doesn't seem as feminine to me as breasts.
Ass, definitely a nice ass. I like something soft to bounce off of while I'm fucking a girl from behind. And I love watching a nice ass riding up and down my cock
Boobs are fun to play with, but when you're really pleasing a girl, you see the ass more. Plus, a girl can't do much about what gave her unless she gets implants... where as a butt, a girl can shape it and get it bigger if she so pleases.
Definitely breasts over butt, although I like both. Big breasts are more in line with my fetishes, and more versatile for sexual and BDSM play, in my opinion. Still like a nice ass though, without a doubt. I'm burdened with being a "whole package" kind of guy.
If I have to choose between one or the other I would go with a nice ass every single time! I just can't resist a girl with an ass and can't help but look