i prefer somewhere in the middle. as long as you can tell you take care of yourself it's fine. but it goes the other way too. there is indeed such a thing as too much muscle. but really in the end abs aren't going to make or break it for me, especially since that's not like it's going to be the first thing I see on him.
Abs are important to me on a guy. I like fit guys with muscles, who like to go to the gym with me. For example a guy has to have defined abs and relatively large arms.(not scary large), but this is just what I like.