CYMA is crap, I saw one take a dump in the first 200 rounds.
TM is good but not king, it's highly overrated, and hard to find in Canada.
G&P looks like a retarded fish.
CA and G&G use the same design and mags. Their parts are different than the TM, but any part except for the mechbox shell which is indestructible anyway can be found through Canadian retailers. My opinion is the CA/G&G mechbox is a much better design, with much more reinforcement, which is one of the reasons I got one.
Yes I am biased.
Guardians of Asgaard - KF32
VFC H&K 416C
VFC KAC SR16 JL Billet SBR
TM FN Five-seveN