For competition, or perhaps self-defense, where reloads are done "on the clock", I much prefer being able to carry the ammo clipped together into a single unit, rather than rounds retained in a speedloader, and do like that the expended rounds are still clipped together after the reload.
I can pre-load as many clips as I want before going to the range, and then never have to deal with loose rounds.
Downsides include the hassle of demooning, but it can be done any time, doesn't require focus, etc.
I don't know that I'd modify a revolver chambered for a rimmed cartridge, unless speed of reloading was of extreme importance, and as noted, that advantage varries with chambering.
I have two .45 ACP revolvers, and even though I have some Auto Rim brass and speedloaders for same, I've never used either.