xarkon
Experienced
Boomerang III.
Meant to provide more information but was doing this from my phone.
One poster has mentioned Looper's Delight. It is a good source of information but does not have current information on some products; for example, the Echoplex is out of production; the Boomerang reviewed on the site is a much older version; etc. LOOPER'S DELIGHT!
Also look at:
Looper Pedal Reviews - Looper Pedal Reviews & Demos
LooperMusic.com | Looper pedals, setup, inspiration, and reviews!
There are others; Google "looper pedal reviews" or similar.
The Boomerang was designed as a live performance tool for musicians who are always going to create the loops on the fly; hence no storage.
The Boss and Digitech units do allow you to create things and switch samples in and out. However, note that there is a serious limitation in the Boss RC-300 - as I understand it, while you can store and access many more than the three loops available for instant access, if you switch over a bank of stored loops, there is a delay before the new loop starts playing. (This is explained much more clearly in some of the reviews. Also, it's possible that Boss has corrected this with a firmware update.)
A fairly advanced performance looper was built by a company called Looperlative. However, their rack mount looper is now discontinued and they now have a pedal-based looper. Home
If you want really sophisticated performance looping, the next step up is to drag along a laptop with Ableton Live. All the looping options you would ever want...but it's a rabbit hole.
I had a Boss RC-2 but really didn't like the operation. Bought a JamMan but have not tried it. I use the Boomerang. While the functionality initially seems complex, it becomes obvious as you use the pedal. It is not cheap; and the additional cost "Sidecar" adds some very useful functionality.
Hope this helps.