I would say it really depends on the individual.
I think i ideally would like to be skinny to athletic rather than muscle bound.
I grew up doing martial arts, and personally prefer agility and speed over raw muscle power.
I have gone to the gym on and off for years, mostly to prevent myself from getting too fat,
but also to keep up my cardio fitness (which is important for martial arts, as well as power).
I observe the types that go to the gym, and i would say that the guys who get the most attention
are the ones who are nice guys, who are athletic rather than the big muscle bound super macho fellas on illegal steroids.
I think that some of those guys who push really heavy weights to build super big and defined muscles look like aliens bug people, and i find them very self obsessed with their looks. If you followed them you would see them looking in the mirror every time they passed one. Super vein.
I think a balance would be better.
I still go to the gym, but solely for cardio and perhaps to strengthen my leg muscles (as my leg muscles aren't as strong as they used to be due to a judo injury). Would be nice to lose a bit excess weight, as i feel better when i am thin.
Not fussed about having big defined super muscles, more into just being fairly slim with a nice shape.
I think what girls are attracted to can vary.
Being slim or skinny isn't the worst shape to have. Super slim people usually can't put on muscle that easy, but they can stay slim. When your young, it may not appear to be a big deal, just weight for 10 years or so, when all the other guys your age will have spent 10 extra years living it up and enjoying domestic bliss.