The question is how many games do you intend to have installed at the same time? I'm running a single 80GB HDD with a couple games installed (MWO, SWTOR) and while I am short on available HDD space (10GB available), this works for now. If you're only going to have a couple games installed simultaneously, then I don't see any reason to go higher than a 128GB SSD. If you're installing more than three or so games at the same time, then I'd probably recommend going with the 250GB SSD when you can afford it.
-Wolf sends