FSX or X-Plane 10?

Just a quick question; I recently got my X52 and am now looking into getting some proper flight games, I'm probably going to get DCS A-10, but I also want a more versatile sim, like FSX or X-Plane. However, I know FSX is starting to show it's age, at least without modifications. I guess what I'm asking is would I be better off with a stock X-Plane game, than with FSX and the extra $40 or addons I could buy with the difference? And is X-Plane as expandable and moddable as FSX?

Thanks!