Genetics all the way.
The majority of the people I have encountered in my 20 years of BBing look worse on roids than when they are natural because of a few reasons. CEO provided the primary document that cannot be refuted, and I would like to give my opinion through my experiences.
I remember when I shifted gears from boxing to BBing in my early 20s I trained at this rat hole. Anyway, there was this guy who trained there, he was probably in his late 30s at that time. He had perfect lines, everything tied in perfectly, striations from his neck down to his feet, full muscle bellies, and everything just popped at you. That dude ate once a day, smoked cigarettes between sets and drank like a fish. When we were done training he would walk over to the local club and drink beer all night while we were home eating chicken breasts every 2-3 hours, and he made everyone in the gym look like they never stepped foot in a gym. That guy was put together like a motherfucker. I'm not talking being between 5'7-6'0 tall and weighing between 160-225 lbs. @ 5% BF (that's small in my book), I'm talking 5'8 225 @ 5% BF. He was drug free; I know that because the only roid dealer in the 50 mile radius of where I lived was a guy who grew-up across the street from me and he said dude never bought a drop or a pill of roids off of him.
Please, I been back to the gym for a month after a two and half month layoff and I'm already the biggest and the hardest in the gym, and I train at a popular gym where there are some serious fuckin' people. It's almost like it's not even fair!
Yaahh for genetics..