I don't do either :) I prefer a well-rounded strength training program using compound exercises; that helps your core tone in a functional way, the way it was meant to work (in coordination with the rest of your body). I also bellydance, which is light to moderate intensity cardio/resistance training, but I do it to learn how to dance, not for exercise (that's just an added bonus, lol).

I would venture to say that most of us who are fairly active have nice abs; we just can't see them because of the layer of fat on top.

My core strength has shot up since I started training for rugby and I love it. BUT!!! cardio endurance is still key to every activity that I love doing. I could never choose.