I've owned a fair share of KWA AEG's in my day and so have pretty much all the members of Delta 9. I'd say 9/10 have broken down just as fast if not sometimes sooner than 'cheap' AEG's. For their price tag, I honestly don't think they're worth anywhere neat what they bring. The have a lot of proprietary little parts here and there that can make them a real headache to upgrade or modify.
Classic Army's LWRC's are supposed to be really really good. I've held them and the externals are truely great. I do thinkg they're electric blowback though, so no bueno on that part. But then again, electric blowback can easily be removed to add longevity to your internal parts.
Other than some random things here and there, VFC's are king when it comes to overall external quality and internal quality. I have a VFC SCAR-L that weighs way less than the Echo1 or DBoys SCARs while having better quality internal AND external parts. The only thing that has broken on this SCAR was before I owned it and the stock piston stripped. It stripped while SoNorUs owned it, and even HE got the gun used, so there's no telling how much it had been shot by that time. Plus SoNorUs likes to shoot full auto a lot.

Most VFC's shoot with a really high ROF too. Maybe not quite up there with stock KWA's, but it's darn close. For about the same price as a KWA, you can get a lighter wieght and more reliable gun with a VFC. If I'm not mistaken there's an Echo1 M4 that is actually a VFC that you might get for cheaper. I think it's the 'Platinum' or something like that.
If I were you and were going to pick from those 3 brands only, I'd have Jon get in touch with Elite Force ( all their high end M4's and even the PDW are VFC's) to get your new gun. The quality is amazing and their customer service and warranty is literally unmatched by anyone else.
just my .2g.