I have used an RC20XL for a long, long time. I am a big fan of it, and have used it for a variety of different techniques ranging from live to studio effects. I stand by this unit whole-heartedly. The Digitch Jamman is good, but I have never used as I have been quite content with the Boss unit. Honestly, I don't really trust Digitech products so I have veered from that pedal as a result.

You are looking at spending around $300 for the RC20XL. You can get the RC2, and those are great for looping as well. I will say, having only one foot switch is a bit cumbersome but you can work past it. For the money, I don't think it gets better than that smaller stomp box. Also, the DM4 Delay pedal from Line 6 sounds great as well and has a good looper in it that I have seen many, many players use.

Best of luck if you not already made your decision. Here is a video of me using the loop station about two and half years ago.

Douglas Showalter - The Quest w/ Boss RC20XL