I live in Bozeman - less than a mile from the MSU campus. I'm on it everyday since our grocery store is on campus lol. Both my kids went to school in Bozeman K-12, and both are MSU grads. For their fields MSU was as good as it gets. I can't speak to GIS however, but I think
@handwerk spoke to that. As to campus life, I don't really know - both my kids were pretty busy, and both worked. Also, they're from here so a lot of their friend-base was formed outside MSU. But both made life-long friends at MSU.
IIRC, you currently live in Connecticut? Not sure where you'd fly from (BDL, BOS or LGA?) - but flights into Denver will be simpler and cheaper than into Bozeman. The cost of living/housing is higher in Bozeman than Fort Collins. I don't know where you will be living once you move to WY, but I'd study what the winter drive is like between both locations. Winter driving in this part of the world can be challenging in the winter (ie, unsafe) so it will pay to know what mountain passes, etc., he'll be dealing with driving home on Christmas break, or you'll be dealing with driving to see him.
When I was 18 my dad sat me down and wanted me to go to the UM in Missoula. I didn't lol. In 1979 when I graduated HS Missoula would have been the place to be. But now, were I 18yo again and had to chose, I'd be in Bozeman and go to MSU. Great access to the outdoors, it's smaller, and even with so much change is still one of the finest Western towns there is - really.
But at the end of the day, the choice should be "from the gut" - you can weigh pros/cons until the sun sets, but making a gut decision rather than a strictly cerbral decision will always work out better in the long run IME - there are just too many unknowns you brain can't asess. Your heart knows things your head can't.
That's all I've got