I currently shoot a .750 bore skeet gun. I've noticed that the recoil (for me at least) is significantly less with the .750 vs the .740. I owned a .740 barrel that I used for skeet for all of one shoot (too much recoil and muzzle jump even though it was ported and I was using a PFS). With the .750 barrel that has been pigeon ported, the muzzle flip is nill w/ 2 3/4 dram 1 1/8oz, and thanks to the PFS i have, the recoil is similar to that of an 1100. I also prefer the lighter weight of the .750s, especially when you put a set of subgauge tubes in it.
My first Kolar (stolen) had the .740 bore and the new one is a .750. The main reason I went with the .750 was the simple fact that almost all new Kolars are ordered that way. They still build the odd one with .740 bore as a specific request. Both guns are / were a joy to shoot. The only real difference I found was that the .740 only liked # 8 shot and the .750 will pound targets with any shot size.
As Ian pointed out, the weight difference makes the .750 barrels more lively. The weight reduction also made up for the extra weight of the new adjustable ribs that are available. The bottom line for me is that I ordered the new gun with the .750 bore and would do so again, but having said that I would not have dumped the .740 bore barrel on my old gun. Both barrels shoot better than I do. Bill Malcolm