Both the 2012 Highlander and Acura MDX have all wheel drive. There's a difference between AWD and 4WD, and lots of arguments about the differences between the "flavors" of the AWD too.
The EPA ratings on the 2012 Highlander Limited show a 2 mpg hit on fuel economy (city) compared to the 2WD models. The rating for the Limited is 18/24.
The rating on the 2012 MDX is 16/21.
So, if you decide to go with an AWD vehicle, the Toyota has a bit of an edge.
I haven't been following the tire debate about the Highlander, so no thoughts there. I do prefer taking my AWD wagon to the ski hill instead of my FWD minivan. The minivan is more comfortable, but I don't put snow tires on it, and it won't handle the hills in snow and ice unless I chain up (and that's a pain).