Id choose the fitter guy. A big dick is a novelty to be honest. In terms of aesthetics, people like a dick more for its "wow" factor than its "hot" factor, if you know what I mean. And once the novelty wears off, then youre stuck with all the problems a big dick guy comes with (pain, being unable to do sexual activities, ect) in addition to his other less than attractive attributes (face, body, personality, ect)
But a guy who is well groomed and muscular and sexy and whose a total package is just hot as hell, no matter what the dick size is. In other words, a guy's overall appearance (hot or not) has a far greater effect on his attractiveness compared to his dick size (big or not). Adding to that is the fact that dick size is mostly determined by genetics (so basically luck) while fitness and sexiness can be done with effort and dedication, which signals to me that this guy got his attributes by dedication and work