I've got a CA SCAR-L right now. The look and feel of the rifle is absolutely amazing. The upper receiver is a sweet solid metal, better than any other I've felt. The lower plastic receiver, as well as the stock, is a super tough ABS that barely flexes when I put force on it. All in all a solid rifle in terms of the feel.
As for the internals I've never fielded it. However, test firing it, it sounds great and is very consistent. Other AEG's I've used have been less consistent in the sound they make with each shot, especially in full auto, where you get some shots sounding a little higher-pitched, some a little lower. With the CA SCAR every shot sounds the exact same, even in full auto.
I've never handled a G&G though. So I guess my opinion is biased lol. But that's my input.
Rifle's up for sale though. Here's the FS thread.. Take a look.
http://www.airsoftcanada.com/showthread.php?t=62102