I've had both (am currently using a Digitech Jamman Delay - ow). I really liked the new 'Rang a lot. The sound quality was pretty good and the pedal action was acceptable. But--I really didn't like that "circular" lighted construct at all. I found it confusing and non-intuitive. And it was time consuming to reassign pedal functions. I may purchase another one now that the new software version is available.
As far as the RC-50 goes, I found that to be a somewhat flakey device, i.e. the interface. A ot of button pushes bending over to setup loops the way I wanted them (e.g. with the proper clicktrack sound). But, maybe I'll get another one day and give it a second chance.
I think the new Jamman w/Delay is an acceptable looper (my favorite has always been the Gibson Echoplex Digital Pro followed by the Electrix Repeater and then the original Jamman). No external pedals are needed for loop-up and loop-down. It does save loops and has a USB port. Quality is very good. The Delay is icing on the cake.
--- On Thu, 9/30/10, Christo Jota <email@example.com> wrote: