From what I understand about the WE mags leaking, it's actually moreso a design flaw from the factory more than anything. If you're handy with fixing things and are so mechanically inclined all it takes is to take apart the mag and apply some sort of sealant (I've seen people use polymer engine sealant that's safe for rubber supposedly) to the square O-ring thing or something like that and it shouldn't leak ever again.
As for the KJW, the only gripe that I've heard people saying is the "rubber band" that sometimes snaps. It's a design issue but I don't know why it's there or what function it serves. I don't even know if you can replace it with something made of better rubber or anything. But other than that it seems like the KJW is probably the best platform if you want low maintenance and good performance OOTB.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE