Originally Posted by
repechage
Good question. The SSC's (in Blue/grey) came first and were very expensive. They did obtain a stellar reputation. At some point the pricey model went away and the GP4 sometimes had a little SSC label, then that went away. The GP4's were considered a durable albeit heavy road race rim, a conservative choice. One went with 330's or the 280's for lightness.
I always heard the GP-4 referred to as a training rim, not a racing rim. But its really just a matter of weight.