I've shot the following revolvers in IDPA SSR:
2-1/2" M19
4" M19
3" M65
4" M64
4" M67 (well, I haven't yet used the M67 in a match, but have it ready to go, pimped out with bobbed DAO hammer, and tested it out in the back yard).
I'd rate the 4" revolvers higher than the 3" and 2-1/2" revolvers due to longer sight radius, which can be helpful with the longer shots (20 yards plus).
I'd rate the 3" and longer revolvers higher than the 2-1/2" revolver, due to the full length ejector rod.
I'd rate the models with adjustable rear sights higher than the fixed sight models, not because the fixed sight models don't shoot to POA (mine all do), but due to the deeper and/or wider rear sight notch that is possible with an adjustable/replaceable rear sight blade, and a file.
And a pinned front sight is helpful...easy to swap out the front sight blade for a fiber optic front sight.
I use Safariland Comp 3 speedloaders, and North Mountain speedloader holders, and have no complaints with them.
John