ID Parts has reported good success with the Mahle unit. I might be inclined to give that a shot.
I bought a new Mahle VNT15 last year for my Golf. It now has about 70,000 kms on it, or 44k miles and it is working like new. No problems yet.
I bought a used Garret VNT15 with unknown mileage for my Beetle. I wasn't spending money on a new turbo at the time as I wasn't sure if the car was worth keeping. Turns out the car is fine, and I've put almost 11,000 kms on it in the past 6 weeks (or 6500 miles). Although the turbo was used, the rotating element was fine. I backflushed oil through the CHRA a couple nights in a row, and installed a new actuator.
My original plan was to install a new Mahle VNT15 later, but the used Garrett is working well enough I'm going to leave it for now and just keep my eye on it.
I think buying a used turbo is OK...as along as you know what to look for in a used turbo,
annnd you are OK with the risk.