Having flown for different airlines and experienced both approach methods, I would agree with most of the others that the monitored approach unloads the Landing Pilot and informs him/her at an earlier stage as to the likelihood of a landing or go-around. The other crew member will be locked on to the instruments and will perform a go-around if there is no clear communication or any ambiguity at minima.
As far as reverse thrust lever handling is concerned, giving control of the TRs to the PM enables the Landing Pilot to concentrate on steering and braking. The PM will monitor the Speedbrake/Spoiler and TR deployment, N1/EPR, and give the PF the amount of reverse required. He/she will also monitor autobrake disconnection and call the speeds. That list shows that the PF is relieved of quite a few duties and can look outside all of the time. The PF can also ask for 'reverse idle' or 'forward idle' if any steering difficulties arise. The same SOP is used for an RTO.
Having said all that, my understanding is that the BA A380 fleet is about to change the SOP and have the PF operate the TRs!
I see the benefit of a monitored approach in dodgy weather, but I think it'd be quite a pain in the rear to do every approach that way.
As to the PM using the thrust reversers...
Does the PM also control thrust on approach?