Check out this website: http://www.loopersparadise.de/
It's german, but you can switch the language to English. Most of the loopers are in that list.
Basically it's a "preset" vs "stompbox-mode" fight. If you use your effects sparingly, here and then you add something, then the stompbox-mode might fit better. It gives you good access to the pedals and true bypass for each one of them.
The preset thing is way easier if you're using multiple pedals at the same time. This comes mainly from the guitar players which might use (e.g.) a compressor, and a chorus in the clean part and then switch to the overdrive plus delay in some other part. With stompbox-mode you would have to deactivate the comp and the chorus and then activate the overdrive and the delay. Impossible in a short time. So the preset mode lets you do this with one stomp.
Some clever types might combine these two - and I find this very intriguing. Reason is the following: you have your presets but then in the live setting you would like to kick in something else additionally. Either you have one loop that is on in every preset with several pedals in it which are deactivated and might be kicked in additionally. But this takes the whole advantage of the true bypass thing if you let your signal through these pedals nevertheless.
So this thing can do both. http://buzzelectronics.co.uk/index.p...product_id=106
You might program five switches to serve as preset buttons, and three to function in stompbox mode. Genious I think. Especially for this price!
I am actually considering buying such a unit, even though I have absolutely no use for it at the moment.