I guess the real distinction to make here is the difference between slim and fit (think professional swimmer) and walking mattress (Arnold Swartzenegger). Most of the HB9 girls (usually tall and thin themselves) I've dated or talked to have told me their ideal body type is slim, defined muscles instead of sheer bulk.
I guess it really depends on your body type. I'm 6'4'' and have a good frame already, so I can focus on keeping my muslces toned instead of bulking up. A smaller guy or someone with not such a good frame might have different priorities.
And at the risk of sounding racist, isn't it true that, IN GENERAL, different races have different ideal male body types? Tall, thin model-type white girls love me, but a short, curvy black girl will usually not show as much interest...I assume she'd be more interested in a well-built dude. And Asian girls seem to emphasize height...these are just my personal anecdotes, I could be way off.