the g&g that I've seen fielded has issues with hitting the mag retainer on certain mags, it has to be moddled (material added) to get the retainer out of the way in order to allow the BBs to feed.
Aside from that, it seems to be about the same. the KA non ultra grade (if that's the one with no quick change spring) should be a standard v6 clone which may or may not have the weird v6 bushings.
I futz with V2s, V3s and V6s. I could be wrong... but probably, most likely not, as far as I know.