I'll play my next campaign as a Barbarian faction with Huge - but up till now I've been really happy with the Large setting. It's big enough to not be puny and small enough not to take too much off the population. I think that the way to fix the scaling is for a future patch to maybe impliment a function for the AI to 'know' when to build units and when not to.... but that's one of those common sense things which the AI seems to be forever without...