Portland OR > Cleveland OH: Take I-80 or I-90?

Hey there! I have made the trip from Portland to east coast a couple of times, but can't remember the 1-90 route going to Butte, MT.
I am looking to see the Badlands and Devil's Tower during the trip east, and then going down to Omaha and finally to Cleveland.
How is 1-90 once you get past Spokane? I am towing the smallest Uhaul trailer available with my '99 Jeep Cherokee (4wd).
I am just curious about those mountain ranges coming after Spokane before Butte. Up/down, and winding? Or relatively smooth with a trailer? I remember going the more southern route through Salt Lake, and it was also a little winding.
Advice? Suggestions? Just trying to make the trip slightly more interesting instead of going through S. Wyoming and S. Nebraska.
Thanks!

Welcome aboard the RoadTrip America Forums!

I-90 east of Spokane climbs gently but steadily to cross the Rockies at an maximum elevation of only about 5'000 feet which isn't bad at all. As with all other Interstate roads, I-90 is built to criteria which limit any slopes to 6% or less, so this is not a bad choice of routes at all for crossing the Rockies. Similarly Interstates have limits on the number and tightness of any curves. There simply is no such thing as a 'steep' or 'winding' Interstate.;

AZBuck