Travelling West to East - I90 or I80

if you haven't been to the Black Hills, S.D., you should plan for two or three days there if you can.
then drop south on 385 all the way to I 80.
There's a great little state park 9 miles south of Chadron, NE.
At Sidney, NE is Cabelas and Walmart if you want to shop for anything.
or...you can take 26 east out of Bridgeport NE and cut over to I 80 on it.
There's a state park at Lake Maconaughy, too.
Ogallala has some old west history. North Platte has a Flying J on the east side of town if you need fuel.
Kearney has Ft. Kearney State Park.. You're on the Oregon Trail all along here.

My husband reported three areas of construction on I90 on his way to Montana. I80 will be ok until you hit Iowa City then it's like bumper to bumper all the way to the Quad Cities.

Well, have you been to Mt. Rushmore, Crazy Horse Memorial, Cluster's Last Stand. I would take I90 into the windy city, then I65 into Nashville. Have a safe trip

Having gone both ways, I would travel I80. I think the scenery is probably equal either way--pretty sparse on both roads. I80 has a bit more traffic and I90 has some sections that will knock the fillings out your teeth--rough. And, I80 is a shorter route as well.

If you pickup I90 at Sheridan, WY, check elevation/grades over the Big Horns as well. If you run I80, you'll miss that heading through Laramie, Cheyenne, etc.