Up until 1 month ago, when I received the CTW MX2, I've been a happy KWA user.
Got a 2nd gen KM4-RIS for $325, stripped some gears in cold weater, put $100 into a full-helical systema gearset to solve the problem, went to a longer tightbore for range and precision, had to get a dummy silencer to accomodate it, then a full-cylinder and irregular spring for feeling, then a turbo motor to get back some trigger response, then braking mosfet for the play-style and I ended up with a $700 replica not counting the external furniture. And I can't kneel with it hanging from the sling, because the silencer will dig in the dirt.
The CTW, externals aside, is "off the box". I don't have the feeling it's broken-in, yet. I've polished the inner barrel a bit and ordered a spare $16 sleeve, because I think some 1000-grit sandpaper will work some miracles there, but wouldn't risk the original without a ready spare. Then there's the issue of BBs. Because of the 6.00 barrel, you have to use only the best brands, like KSC or TM, otherwise you'll get jams and possibly gear damage. The KWA on the other hand, even with a 6.03 tightbore will happily shoot any kind of china-shit plastic balls.
Trigger-response notwithstanding, both will have the same precision upto 150 ft (50 m) on semi. Going to 200 ft, the modded KWA gets an edge, prolly due to the longer barrel. In burst or full-auto mode, the CTW wins hands-down with a lot less spred then the KWA.
Off the box the Celcius beats KWA, if you use best quality BBs. Upgrade-wise, until the Celcius M16 parts become available and we get a long-barrel choice, the KWA SR-series seem more attractive. Game-wise, you're a lot better off with a Celcius or Systema then any other ChinAeg.