most CA guns, but not all, are clones of G&G. They usually have the same externals except for the internals w/c as you've said CA has higher FPS.
Base on my experience (I have 3 G&G guns; CQBS, M14, UMG), G&G builds good/high quality guns. So far I have them for 2 years now and I haven't got any problems with them except for some lose wiring with the motor because I changed it.
since you are going for the m14 ebr w/c i would assume is somewhat similar to my m14, let me start by telling you that when I first used it even at 370 fps it was very very damn accurate! I think one of the pros of G&G guns is its accuracy out of the box.
with regards to your idea of having higher fps for better range is somewhat true, but 370 vs 400fps? 30 fps is not much of a big difference. I would suggest you upgrade to 550-600 at .20g bbs, then use heavier .28 - .30g bbs for better range and accuracy. so either way, CA or G&G, I strongly recommend you upgrade the internals. I'm pretty sure the 400fps CA won't outgun the 370fps G&G.
you also have to remember in airsoft, higher fps doesn't mean better accuracy. I've shot a 500fps mp5 gun and its accuracy is like hell!
finally my last note. Once you get the gun DO NOT FORGET to tighten the screws on the front sight or just use some kind of permanent glue. I know a couple of people who lost their font sight.