I would have to go with PLO. Probably the easiest game to make a transition to from hold em. Also the game that I think you can make the most money from. Just my opinion.
Considering that in PLO most hands are at most 60-40, I don't think PLO would be a candidate for least amount of variance.
I would say stud hi gives the biggest advantage to people with the best memories. Ex. If you can remember every card that was dealt up before people fold them = HUGE adv.