Not sure of the Acadia, but many of these small GMC vehicles use the Versatrak AWD system. This is NOT a full-time AWD system. This system sends power to the rear wheels ONLY when the front wheels are losing traction. Works fine for pulling out of a slippery situation in low gear. However, I doubt it will ever function once you get rolling. The front wheels have to spin significantly faster than the rear ones for the AWD to kick in. One is not likely to push a vehicle to that point at highway speeds.
We have Versatrak on both our 04 Vue, and our 02 Silhouette. The full time AWD of our old 97 Astro was superior.
You should be considering 4wd vs 2wd, and choosing a vehicle that offers that. If you are towing and need the traction, 4wd is superior. It works just as well at highway speeds as in low gear.
We live in Canada, and we winter camp. I wouldn't do it without a 4wd vehicle. This not only improves your pulling, but also your braking. 4wd vehicles typically lock the front and rear axles together through the transfer case. This prevents the front wheels from locking up before the rear ones do. It also distributes engine braking over all 4 wheels. That is important coming down a snowy grade with a trailer on. I know.