Beware- while Looptree seems very cool, it appears to have very limited MIDI support.
The reason I love Loopy is my setup performs basically like a Ditto on steroids. It's a small chore to set it up the first time, but once there it's stupid simple to use. Even then I feel like I'm only using 10% of it capability.
Fwiw, another cool analog style looper is Ostinator.