Had new tires installed yesterday.
I went with Pirelli Scorpion AS 3+ because of the excellent reviews on Tire Rack. 245/60 R18.
I've only put about 50 freeway miles on them so far but they are much quieter (both at steady speed and while impacting bumps, ruts, etc.) than the OEM Michelin Latitude Tour HP I had before. Turn in from center is also more responsive than before, smaller movements of the steering wheel cause the vehicle to shift direction sooner, more fitting for the MDXs athletic nature. Previously I had great experiences with the Continental ExtremeContact DWS 06 and 06+ (MINI and Q7), but they aren't made in the proper size for the base wheels, they were more expensive, and I rarely drive the MDX hard enough to appreciate the additional grip an ultra high performance AS tire would provide anyway.
I didn't really think much of the Michelins. They weren't great at anything in particular but I never had complaints either. They got me through plenty of dirt and mud-covered roads just fine, but spent most of their time on dry pavement in the Southwest so their supposedly poor winter/wet performance (based on TireRack reviews) went unnoticed by me. I got 58k miles out of them which is rather good I think, but I would have replaced them a year/10,000 miles ago if I had rain or snow to deal with on a regular basis. The tire noise wasn't an issue for me because I became used to it. I couldn't switch back now knowing how much quieter the Pirellis are.