I traveled both 2 years ago and highly recommend the Dempster if you were forced to pick one. First, the Dalton is purely a "Haul Road" for the oil trucks. So tons of stones kicked up, and dangerously fast truck drivers. The Dempster was nearly empty, we passed maybe a dozen vehicles max from the start all the way to Tuk. Not counting the fuel stops, etc.
The biggest plus to the the Dempster is that you can camp right on the Arctic Ocean beach. And do a polar bear plunge without scheduling a tour to pass through the oil fields. If you go during a time where it isn't running, you don't actually get to travel all the way to the coast and it feels a bit cut short. Tuk is a great little town, we talked to some locals, and were invited to witness them pulling in a whale and watched them butcher it and prep it for processing. There isn't any services that were open when I arrived, but an overpriced camp site on the beach, 50 CAD was well worth every penny.
As others have said, make sure you have a spare tire. And be prepared to use it. I had 1 flat and due to it being an odd size, I wasn't able to find a replacement until I got to Vancouver. I could of ordered one in Anchorage, but didn't feel like waiting for a week for it to arrive.
Oh, and the Mosquitoes were absolutely unlike anything I have ever experienced. Found myself driving longer than I planned everyday because I couldn't do much outside of the truck or camper without getting swarmed with them. Pack insect nets that go over your hat and tons of bug spray.
If you have any questions feel free to reach out.
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