I actually like both designs. I think the Highlander is more edgier looking while the Acadia is very bold and has attitude, as well as being easily distinguished on the road. It's mostly interior function that will be the deciding factor for us.
I just wish the Highlander offered HID headlamps in a projector assembly, instead of only halogen with high/low functions in the same assembly. I think it looks really cheap and makes it look like they cut corners on the design.
I like that the Highlander has true rear auto climate control, as well as push-button start, and that you can open the liftgate glass separately. My parents are horrible when it comes to cargo management in our minivan, as they put the stuff in removable bins, and forget to put on the cargo net, so a couple of items end up falling whenever we open the liftgate. I also believe that if you purchase a hybrid, that you get $1000 or $1500 (I forget) back from the government.
Now that the features and options have been officially released for the Highlander, I say I'm going to choose the Acadia. I really want the dual sunroofs, as our minivan seems really cramped inside, since you cant roll down the windows in the second row, as well as the lack of sunroof. I also want the HUD, since it always feels like we go way too fast whenever my dad drives, so I constantly want him to be aware of his speed. Remote start is a must for us in Canada, as well as parking assist. I also prefer the 2-2-3 arrangement of seats rather than the 2-3-2 in the Highlander. OnStar is another deciding factor, and our Pontiac/Buick/GMC dealer is already fantastic, so for us, Acadia has won, but the Highlander isn't off my list yet