Worst is pretty easy - Socom Gear M9A1. Rattled like a bag of spanners, mostly vented gas at random points through any given mag. No discernable accuracy. Looked nice though.
Best for out of the box range and accuracy has been my Cyma M14 SOCOM. Whether it stays that way remains to be seen, repairs are underway after my tactical tumble.
Overall best though is probably my Specna SA-A03. Bought it bloody ages ago when SA were a new thing and still OEM'd by E&C. It has one of the old red Maxx hop units with the tracer bits, ML rubber and a ZCi barrel, and a Gate Titan with an Ultimate Infinity 30k motor. Anything else is cosmetic but it's been ridiculously reliable, decent range and good accuracy.