From what I have heard and see, and from my first hand experience with the JG one, I can say it is not a bade choice at all. I can't decide for you since I don't know the CYMA one, but the JG one, especially the newer version as MaciekA said, is a good pick.
EDIT: That particular retailer is running a mystery box, with the lowest prize being a JG G36c. It's something you might consider.
(Also, remove the link, they are not allowed in this section as per the rules

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EDIT 2: This version is NOT the newest one. Unless I'm mistaken, of course.