I'd get while the getting's good. Fucking cocksucker Vegas shooter got 'em banned here.
Beyond price there's some differences between the Franklin and the Fostech. You need a full-auto carrier with the Fostech, but that also makes it so you're not outrunning the carrier. Not sure it's guaranteed, but harder to do than with the BFSIII. So heads up if you're thinking about swapping around uppers with one of them. For the Echo, there's aftermarket springs that supposedly make a big difference. Am told the disconnecter spring (I think) is the one that makes the real difference. I put one in due to the reviews but haven't tried out the trigger yet. Couldn't tell you what it was like before the spring change.
I suggest pairing one with a .22lr upper and a 50 round drum. That may be picky with ammo. I've seen good results with this.