Sometimes I have some research-level mathematics questions; as I have read in "What's the difference between MathOverflow & Mathematics.SE?" and similar questions, I know that I can post on both the Math.SE and MathOverflow societies. But there is a trade-off; the former has a larger society and also in theory has lots of users in common with the latter, which I can user hints of all of them.
But in the latter, I suppose, the users are all the ones who are prepared for such research games. Which one do you suggest in this trade-off?
My own choice, up to now, is to use MathOverflow, in which the users' business is research, because I think that even the users of both sites, when they are on Math.SE, are not searching for research as serious as what they do on MathOverflow.