We try to maintain an equal relationship with all of the hardware vendors. As such, we don't try to promote one more than another.
However, generally speaking you will get better performance by paying more money.
In the case of USB vs WIFI you won't get much better performance. WIFI costs more but it's mainly for convenience sake. If you don't mind plugging in your laptop to the OBD-II interface, USB is a cheaper deal. Also, USB is for Windows only.
An incomplete list of compatible hardware can be found here: http://www.palmerperformance.com/hardware/index.php
However I don't recommend the OT-2 at this moment because there is an identified bug with some cars.