Hi OP. Current PhD student here. I was in this position during my application season. Several people have answered your second question, but not your first, so here's my best shot:
Unless you have outside funding (think NSF), Michigan gives every admitted student a standard package.
OSU's funding structure is a bit different. Unless it's changed in the past few years, the graduate school makes the funding decisions then sends them to the dept. If the graduate school thinks you are a competitive candidate, then, you'll likely receive a better offer than others in your admitted cohort. This, obviously, has its benefits and drawbacks.
Additionally, the cost of living is pretty different between Columbus and Ann Arbor, so you'll have to take that into account as well if you find yourself in the position of making a decision between both places.
So the answer is, really, that it depends on what you receive from Ohio State if the funding offer is better. Feel free to message me if you have any additional questions.