Seeking Recommendation For Routing Great Falls, MT to Coram, MT

[jack45]

Coming out of Great Falls which would be best; Highway 89 up to Route 2 over to Coram, or to stay on Interstate 15 up to Route 2 than over to Coram?

How are the grades and roads? Is one more scenic than the other?

Traveling in 40ft MH towing a vehicle.

Thanks, Jack Ricardo