Joel,
There are many, many more types of Bermuda then the ones you mentioned. Yes, those are some of the more common varieties, but there are many others in use today. Anyone interested in turf grasses and how they are graded in trials should go to
www.ntep.org, the National Turfgrass Evaluation Program's website sponsored by the USDA and the growers. Interestingly, GN is not submitted for trial.
Also, in most cases even a trained supt. would have difficulty differentiating between most of the vegitativly planted hybrid bermudas. Availability, cost, purity, will usually be what drives selection. All bermudas can be maintained lean and mean, we rarely see it because a lean bermuda is not a pleasing color and thus they are almost always over watered and over fertilized. If anyone played on a bermuda and thought it was a firm, fast playing surface, IMHO, it was a result of how the grass is cared for more then the variety.