"I suppose its what you feel comfortable wearing..."
I gotta say, I've never understood the compulsion we have to tell brother watch fans/collectors "What they need," based on their wrist size or the "What's appropriate?" template that resides in our own heads.
I have an original Russian diver that's about 60mm, and I get a kick out of wearing it a couple times each year. It gets lots of favorable comments, and, on a bright day in the mountains, I can signal rescue parties with it, when I wander into the wilderness and get lost.
I'm 6' 6" tall, weigh 250, and the only things I lift, voluntarily, have been cooked or chilled.
I don't think I've ever felt the urge to tell somebody his watch looks ridiculous on his wrist, but that could happen, tomorrow, I guess. Never say never.
Meanwhile, I favor the broadest selection of sizes possible.