I have both GSR and P220. They both shoot great; however build quality of GSR does not match P220.
GSR was pretty loose and rattled from day one. You can also see tool marks on both frame and a slide.
P220 on the other hand is perfect - fit, finish attention to detail.
Again they both are great shooters despite GSRs quality issues.
I think that for the money you can do better with other 1911s.