Do bear in mind that the current version of the Bluetooth unit seems to be regarded as Crap. (only SAP phones, limited contacts etc.) The next generation will be better in some ways, but still seems uncertain. I'm waiting because I have a UHI car anyway, but If I'd kmown it would take this long I would have ripped it out and fitted a Parrot unit.
Having used both I would say that the Parrot set up is significantly better in most respects - the Comand integration is nice and the Audio on my current setup (UHI with Nokia 6230) is slightly better than the Parrot. (Which I would guess is just the MB integrated microphones)
If you don't have UHI I would say that fitting the Parrot is a no-brainer - Its much cheaper and far more flexible