I have a Diamond Pro cut. A new pool hall opened in town with all new GC IV's and there is no comparison. The GC has much larger pockets, will take a ball that hits the rail much higher than the Diamond, has cushions that are far too lively and has the metal tops on the pockets that tend to scratch the cue.
The Diamond is much more a professional table and is much more of a challange to play on. You have to hit the ball right in order to make the shot. No gifts. But fair. No shimming of the pockets.... the cushions are cut correctly.
Do it right the first time and get Diamonds. Buy the one's they play on at the Open for a discount. A big bonus is that the company was built by, owned and staffed by pool players and is small enough to provide real service direct from the factory.