I've got a 625 that I shoot USPSA major 45ACP loads in (because I'm lazy and don't want to make different loads for IDPA), as well as a 686 and a Model 19 both of which I use with speed loaders. I love shooting the moonclipped 625 because, as Gregg K pointed out:
and I don't mind being lazy since I'm just in this to have a good time shooting with friends.
Even so those lighter guns, the 686 and Model 19, are both fun to shoot and they do seem to transition better. The quicker transitions really become apparent when my wife shoots. She loves the Model 19 (there are rumors that she thinks it's HER gun... whatever...) over the 686 just because it is lighter. Apparently at 105 power factor the extra weight of the 686 isn't helping her.
Even so a bad moonclip reload is still not so bad when compared to a bad speedloader reload. Sure you can spew live rounds all over the place but the worst is an ejected case getting hung up under the star. I've seen that happen to several shooters and it's a real time killer.