I'm quite certain (personal observation and have been told by many) most women prefer lean, muscular, in-shape guys vs the doughy, undefined, "big" guy. And yes, abs are a HUGE turn-on for women. Women will check out your ass to look for a trim waist. Don't be afraid to wear some nice fitted jeans and a tighter v-neck t-shirt or similar on your next date. If you have pipes, wear something that shows them off too.
Staying in top physical shape means you take pride in your appearance, feel good about yourself, aren't afraid of hard work and dedication, and have high standards for yourself which translates to every other facet of your life--and women know this, especially the high-quality ones.