I don't know much about the WE's, but the biggest complaint with the KJW is the lack of aftermarket support. But the gun shoots quite well out of the box to begin with.

It sounds like all the information you need has been said, and re-said. It's up to you now to decide which platform you like better. Forget about "50/50, 40/50" or whatever anyone says, it's your money and you should use it on the platform you want. IMO, I'd go for WE just for the fact that aftermarket support is there, if you ever have an issue. No gun is to last forever and never break down. When it does kick the can, do you have replacement parts available to you?

Earlier I would say KJW but WE is really starting to step it up so personally i would go with a WE now. I have a WE G36 RAS i have had no problems with it and it's truly is a great gun i also got a KJW M9 and it worked great but in about 2 mouths of little use the valve cap broke

also with WE there are a lot of upgrades and parts almost everywhere to get for your gun

I'm a KJW owner. I choosed it first because i'm not very a handy guy and they said it was reliable right of the box. Now I get more experimented with GBBR and more and more I'm thinking getting WE mostly for those 2 reasons:
-Realistic recoil
-The fact their many replicas working with the same stanag Mag. With KJW you only have one
WE seems very dynamic to release new models every year. I was expecting the same with KJW and i'm very disapointed after 2 years.