Profit per Standard Deviation

(I'm pretty sure that this is the wrong forum, but I think I'm more likely to get a very nice response here.)

I wanted to compare the profitability of different types of poker, and I think the proper way to do it is to compare profit with standard deviation--essentially return relative to risk.

I'm a little unsure of how to properly define these numbers, though, because I'm not sure what constitutes a trial. It seems absurd to compare the standard deviation per hand of a ring game to the standard deviation per MTT.

Any suggestions?