CA have 2 lines - the Sportsline, and Proline.
CA Proline are the metal, heavy duty guns with reinforced internals and such. They're the "good" CA guns.
CA Sportline are their relatively new cheap line of guns. They have regular, non-reinforced internals and lower quality metal out parts. Also, most have plastic receivers, although they now make Sportsline guns with metal receivers as well.
If the CA you're looking at is cheaper than a G&G, then it's definitely the Sportline. I'd go with the G&G. It costs a bit more, but you also have a better quality gun, at least in terms of internals. Externals are about the same grade as the CA Sportsline.