The Canadian teams tend to have a lot of undrafted former major junior players that either didn't get a pro contract or decided that after essentially playing semi-pro for several years that it would be better to get a degree than spending several more on overnight bus trips in the ECHL or SPHL. The roster is usually filled out with graduates of eastern Canadian junior leagues. The teams tend to be older, bigger and more physical than we usually play, but Division I teams generally win about 80% of those games. They've also played 4 games so they should have less early season sloppiness.
The Union game will be interesting just to see whether their coach can get them to take a step forward in year 2. Looking at their recruits there aren't any that jump out as difference makers but perhaps a year in his system will start to gel in year 2. Obviously any game against a rival, even an exhibition game, will have greater intensity, but the quality of play may be spotty as they've only had intra-squad scrimmages to date.
I'd probably go with the Union game unless you plan on attending one of the league games or the Mayor's Cup against them, in which case Guelph might be a good change of pace.