Revolvers that use auto pistol rounds with full-moon clips are much faster to reload than guns demanding conventional push/twist speedloaders. Auto cartridges are also generally shorter that revolver cartridges (9mm vs. .357, for example), and this also makes them faster to load.
I like the idea of 9mm and .45 ACP revolvers. The faster/simpler reloading ameliorates at least one deficiency of the revolver compared to the auto as a fighting tool. If I had to carry a revolver for defense or duty, rather than my preferred Glock, I'd vastly prefer one using an auto cartridge and moon clips. I'd probably choose 9mm, since .45 ACP revolvers are generally pretty big and unwieldy (though I used to have a Smith 625-2 that I liked).
I don't really see a disadvantage to the moon clips, unless you are dextrous and cool enough to accomplish a "tactical" revolver reload under fire. Even then, I guess you could carry a combination of full-moon and half-moon clips.