The LTX M/S is more of a rugged all-weather tire, great for driving in severe weather and light off-road use, but with excellent road handling manners. I've never had a problem with road noise, though they are slightly noisy on grooved/rough pavement, but lots of tires with water channels are.
The Latitude Tours are definitely a road-only tire, probably designed for the majority of people who only use their SUV as a station wagon and don't need the mileage and rolling resistance penalty of any rugged capability in their tires. Probably a good thing for the newer Explorers.
If you just use your SUV the same as a car, you'll probably be happy with the Latitudes.
There's also the Michelin Cross Terrain SUV, which is a toned-down version of the LTX M/S, also more oriented to daily-driven SUV's that see mostly fair-weather pavement use, but with more capability in inclement weather than a car-like tire like the Latitudes.