I've owned 2 Gold Cups and shot/fondled (er, inspected) a friend's GSR. Sold the GC's for other things, not because I didn't like them.
GSR - good all around gun. Very accurate, reliable, and well built. Fit and finish are very good. Holster choices are very limited. Sig stopped making these guns due to some sort of production problem. Hope they can sort them out.
GC - there are many versions of the GC out there. I don't care for the Elliason rear sight on the older models. Sharp edges, problematic roll pin. But remember, this was intended to be a bullseye-type gun, not a carry/duty gun. The GCs with the Accro and/or the Bomar are a much better choice.
Colt is building some incredible guns as of late. Get the GC. You'll like it. Get it in blue. If your FFL has more than 1 in stock, compare them to find the best one. Also, do NOT completely disassemble the fire-control parts in the frame or you'll be searching for a itsy-bitsy spring. Buy some Wilson combat mags, and shoot the snot out of it. You'll like it.
SF
SVI .40 doublestack
LB PII w/ 1.5" guarantee
Colt SCG
Colt DE, custom
Colt LWC, custom
SA MilSpec, custom
Colt 1911 and AR15/M16 armorer