They are not any different, aside from the finish. RC's on a GLI are painted BBS silver. RC's on the 337 were shot peened with a clear coat finish.
04.5 GLI's are a dime a dozen on the East Coast. Pricing has come down quite a bit on them, but you will still pay close, or more than KBB value for one that is clean, with low mileage.
Good luck finding an unmolested 337 for the same $$.
20th AE's are nice too, and have all of the options you are talking about, minus the RC's, but hell... its only 20 bolts to change those out.