I can't comment on the Pirelli P-Zero Nero M&S tires, but from my experience with the P6 allroad tires on our 2001 allroad, I am not impressed with the mileage out of those tires.
The allroad OE tires wore out in 12,000 miles (I think the treadwear rating by Pirelli was 240).
When they wore out, I went to the Michelin Pilot Sport A/S tires (treadwear rating 400 by Michelin). Michelin does consistent treadwear ratings across their tire spectrum (so a 400 on one type of tire should yield the same results on their other tires).
I had MXV4's on our Accord that went 40,000 before they were tread worn. I put 14,000 on the Pilot Sport A/S before I turned the car in and they showed little treadwear.
You have to balance the cost difference versus treadwear to see if the mileage on the Michelins justifies the additional cost.
My 2 cents