Compare tether Blu and tether Wifi

tether Blu is harder to setup, I would recomend using tether Wifi if you have never setup a bluetooth IP Network Connection before.
tether Blu uses less power than tether Wifi
tether Blu only allows one connection tether Wifi allows multiple
tether Blu is now just as fast as tether Wifi with the recent bluetooth updates in Android 1.5 (cucpake).
tether Blu uses bluetooth pairing for security, tether Wifi only uses MAC filtering no encryption. tether Blu is more secure.