Based on the small amount of time I've spent in Fargo and Grand Forks, wind is always going to be an issue. For that reason I would suggest something with drop bars. It sounds trivial, but the ability to lower your torso even just a few inches can have a huge impact on your aerodynamic drag. It may not be comfortable to ride around campus on the drop bars, but if you are riding anywhere out in the open where the wind can really get going you will notice the difference.

As far as size is concerned, I would suggest riding as many bikes as you can. Our local Scheels has a couple of trainers for indoor test rides, I am guessing that monster of a Scheels in Fargo has plenty of setups you can try. As you mentioned, you really should try different brands and different sizes within each model. I ended up buying a frame that on paper is too small for me, but I found it to be the most comfortable. The point is that it's difficult to know what bike is going to fit you best until you try a few on for size.