Realistically, good competitive revolver shooters, under match conditions, can reload with spring-loaded CompIII or Jetloader speedloaders in about 3 seconds even. That's the time from the shot before to the shot after the reload. And those
shots hit their mark, too, i.e. in the A- or down zero- zone. Very good competitive wheelgunners can do this in under 3. Anything under 2.5seconds (with good shots before & after) is wicked
fast. A moonclip would likely take about half a second off that. In contrast, twist-type speedloaders like the HKS probably add
about a second or more.
Below is a vid of me and a 2.75 second speedloader reload, which is right around my norm. FWIW, I'm a Master level SSR shooter. If you're just starting out with your reloads, focus more on getting the movements down smoothly and getting good hits before & after, then
start thinking about speed.
If speed is your gig, the right gear is important, but the real
secret is a metric boatload of practice at home with dummy rounds. Moonclips, for instance, ain't gonna get you there on their own.