Whats the difference between these two Revolvers besides the big price difference?

Well first of all airsplat is way cheaper than most stores, but it looks like the one from airsoftmegastore is much more solid that the one from airsplat. I would go for the megastore revolver. By the way unless that is your primary I would cut that barrle down a bit. I personaly carrie and M9A1 as my side arm with a cut of revolver in my boot, it works great as a back up