Both routes are nice - the soutern route is where you have less traffic and will not come across many metropolitan type of cities where the northern route is more common. You hit cities like philly, detroit, chicago,
After chicago you can do they real north - like Montana and Dakotas or you can do they usual route.
Yep! South def has less traffic.
Have traveled by road through Ga-AL-MS-LA-TX and there is not much to write home about frankly.
It was a long time ago but we drove from AL to Seattle, WA - went through TN, Kentucky, the Montana, Dakota route and really enjoyed it. On the way back we came through Utah, KS, Missouri. We didn't stop in a lot of places on the way back so didn't get to check out what was out there.
I would recommend the Northern routes just because there is more to see.
In the South, the southern states pretty much all look the same to me unless you want to stop in New Orleans.