Out of the box the G&G (depending on the line/grade) shoots roughly 300-310 fps out of the box. But their quality control and build material are very good, they even designed some of their own systems ie. the blowback models mp5 and m4.
While the JG on the other hand uses a cloned systema gearbox and has very high quality parts even though it is a china clone company. Even their quality check is getting better and out of the box the JG's usually shoot about 370-400fps.
"Don't you know the first law of physics? Anything fun costs atleast $8"