The difference between them all is binning. The GPU cores in the FTW cards (or G1 gaming or Gaming Z or top tier, most expensive cards) are cherry picked for performance and thermals. The tier below them, a.k.a. the average aftermarket card (SC or SSC, Windforce, Gaming X, etc.) are the GPU cores that weren't rock bottom, but weren't good enough to make the cut and be top bin. Stock, like the reference, SORRY, Founder's Edition were not sorted at all.
The price difference will show, usually around $75-100USD between bottom of the pyramid and top binned chips.
The performance difference is negligible unless you plan on chasing world record overclocks on LN2. If the GPU is being used "as intended", there is absolutely no difference...