I have a can of H110, but I'm just a much bigger fan of 2400 in magnum handgun applications, especially the .357 Magnum. 2400 is much more flexible, and gives up little.
As far as the barrel length, I've owned both 4 and 6 inch L frames in the past, and while you CAN carry the 6, I found myself reaching for the 4 inch most of the time. With regard to accuracy, both guns will likely be equally accurate, but the longer barrel is easier to shoot to the standard it's capable of. The sight radius is some 30% longer with the 6 inch barrel. As with all things, it's a compromise of ease of use and carry versus velocity and sight radius. Which one matters most is something only you can decide.