I prefer tank top myself.  Men's armpits can be pretty smelly.  Short-sleeved or long-sleeved leotards start to really stink on me really quickly.  It's even worse than with T-shirts because the leotard is closer to your armpit and just soaks up all the sweat.

I'd guess that's probably why men don't usually wear long-sleeved leotards.  But if you want to deal with the practical issues here, there's no reason why not.