In the three that I've used, I've found that the Repeater has the "truest" (I don't know what word to use here hahaha) sound. There are some hum/clicking issues with the Repeater from time to time, and it is a tempermental box to be sure. But, unlike the 'Rang and the Boss RC-20, there is less of a tendency to compress or distort the quality of tracks the more you overdub (layer new tracks on top of existing tracks). Then again, for some people (like violinist Andrew Bird), the particular sound of the RC-20 really fits right in with his whole musical aesthetic.
If you are a beginner, then I don't think there's a need to go plunk $1500 on a Looperlative. Find something to get your feet wet, see what kind of sounds come out of you, and go from there.
I hope this poorly worded e-mail and my dead brain's inability to find the right jargon have been helpful! Good luck!
Best wishes,
Ben