We've done both routes, several times. We live in Virginia and have spent the summers in Montana (about 90 miles south of Glacier National Park) for the last 10 years.
No doubt, I94 would be quicker, if that's your goal. On the other hand, we've found that dawdling along has been much more fun. Lots to see and do along US-2. There will, likely, be construction either way. We didn't do any night driving (in the summer, that far north, it isn't dark until 9ish), so didn't find wildlife to be a significant hazard.
The route selection, it seems to me, is pretty much individual preference driven unless you're in a hurry.
I do have one strong suggestion. Make your reservations in and around Glacier Park EARLY.
Things get booked up early. For much of this past summer, admittance to the park was by reservation for entrance between 6AM and 6PM. After 6AM, unless you had reservations for in park lodging or one of the boat tours or Red Bus Tours, you were not allowed entry into the park. Even then, it was crazy crowded. Here's a link that describes the crowds: https://www.nps.gov/glac/planyourvisit/crowds.htm
We grew up near Glacier and have been visiting regularly for more than 60 years. For the last 5 years, it's just gotten to be very, very crowded.
I don't, in any way, want to discourage you from visiting Glacier, but, just be prepared to make necessary accommodations for the crowds. Make reservations early. I'd very strongly recommend that you consider one of the Red Bus Tours: https://www.glaciernationalparklodges.com/red-bus-
The 2022 tours have not been finalized and reservations are not currently being accepted. When they do become available, they will book up very, very quickly. If you scroll to the bottom of the web page for the red Bus Tours, there's a link that will allow you to "SIGN UP FOR GLACIER NATIONAL PARK LODGES' EMAIL AND KEEP UP TO DATE WITH THE LATEST NEWS." That may get you email notification when the 2022 tours are available for booking.
P.S. Even from southwest Michigan, my choice would be across the Mackinac Bridge and thru the UP to US-2. Yoopers are, for the most part, pretty friendly.