How you work out your abs determines how they'll appear in the long run. Not only are the type of ab exercises you do important, but also the frequency with which you do them.
If you want lean abs without the hulking six pack then working on two sets of crunches almost daily is the way to go. But to get those muscle builder abs, you have to blast them on one day and then let them rest for the rest of the week.
There is a lot of confusion about ab workouts, should you do them every day or just once a week? The arguments go on endlessly on bodybuilding forums everywhere and the reason is that there is no right answer, it depends on your goals!