I changed the bezel on my 8926 from the Seamaster to coin edge after I took it in for service and the guy put the entire watch into cleaning solution and bleached out the insert. The clicker was gone also and the bezel was frozen up. I don't think I'll be taking any more watches to him...
I had an old Submariner replica bezel that fit perfectly, so I put it on and now I like it even more than the original.
The coin edge is easier to turn, looks better, classic, I guess all of the above. If you're going to copy a classic, go all the way...the way that the original designer intended it. Frankly, the "seamariner" look was one of my only hang-ups with the watch. Besides, the omega bezel was so darn hard to manipulate.
I did get a replacement watch for my mental distress at a sizeable discount. So the guy did make it right, to my satisfaction. I got a 8927 TT with the seamaster bezel on it. Of the two, I prefer the coin edge, and when I pick up the 8928 (my next Prodiver) I'm getting the original.
For all the above reasons, but mainly for the grip. I have 2 Pro Divers, one with each bezel, and the coin edge is so much easier than the scalloped shape. But i don't dislike the look of the scalloped, and it's one more thing to add variety.