I guess in a way I'm just asking how variance is calculated in the first place?
See this
link for the definition of variance. Generally speaking (ie mathematically incorrect [img]/images/graemlins/cool.gif[/img]) you get lower variance if you finnish in the money more often. A more correct mathematical explanation would be to say that you lower your variance if you get your results to stay closer to the mean (which is quite obvious [img]/images/graemlins/smile.gif[/img]).
However, I'm still assuming that you are talking about a variance that's associated with win-rate or ROI. You could also specify a variance for the probability of finishing in the money, but I don't see how that would be useful.