I'm a home-only player and use a looper that's built in to a ZOOM G5n multi-effects, but I've also used a BOSS RC-3 and a TC Electronic Ditto X2. I think BOSS (RC-30? and possibly others) do loopers with multi-tracks, but the ones I've mentioned have no separation between the tracks, or layers... other than to allow 'undo' and 'redo' of the last recorded layer. Unless you really want to separate the tracks for recording, the simpler loopers are great fun and all offer similar functionality. I use the G5n because it has unlimited overdubs, 80 seconds mono looping, or 40 seconds stereo (either of which is enough for me to practice with) and it has the option of 60 rhythm tracks that 'quantize' the loops - I use the simpler tracks, more like you might a metronome, purely to assist with timing.
In general, I have come to prefer loopers with a button switch, as opposed to the spring pad of the RC-3, they just feel more precise. The G5n can be set up to give you a two button looper, like a Ditto X2, but I'll probably add a TC Ditto X2 to my set-up if I feel the need for longer looping times. The Ditto only stores one loop [might be two... can't remember] so you can't advance to multiple loops, but the likes of the RC-3 and Digitech Jamman store many many more... I can see the advantages of this for a performer, but for home use it's just one of those things you'll probably never really need. Also, you can store backing tracks on these loopers, but I'd use my other devices for that, where I could more easily access my libraries.
One good word of advice I read recently was, you'll probably never need a lot of the functions of some of the fancier loopers, so just start with something simple and take it from there.
A decent looper starts at about £65.00 (the basic one button Ditto) or £120.00 Ditto X2, RC-3.
