US 34 is definitely slower than I-80. It goes thru lots of small towns. Not really that much difference in miles.
Can't say it's more scenic than I-80. It goes thru Iowa. You'll see corn either route.
If you want to see something other than interstate then US 34. I use to live along US 34 and have driven it alot. I've seen that area so it doesn't matter to me to see it again. I'd take I-80.
Camped in every state