gglass, i see that you shoot at SJCRC as do I. Maybe i'll see you around sometime with my new GSG 1911-22. It sounds like you have some experience that would be nice to aquire on this gun.
Ok, the colt is not made by GSG. It's made by Umarex; however, both are in Germany. The colt has a fixed barrel and is based largely on the p22 platform. The GSG has a hybrid barrel system. It is pinned/screwed, but is still removable. Colt mags are nicer and are 12 round vs 10. Both are very nice pistols.
Walther is the parent company of the company that makes the colt one. GSG also makes the Sig. I wouldn't be afraid to own either. But i already have too many 22lr handguns.