I drove both routes a lot.
Atlanta is awful, but as long as you try to avoid rush hour periods it is manageable. The cops are thick from McDonough on south. Those towns seem to survive off citation money so don't speed.
I like taking I-65 through Alabama. Traffic isn't bad and neither are the police. Even Birmingham, with all the construction on the interstate, isn't bad except at rush hour. And even then it's won't give you road rage like Atlanta traffic.
Those fools can't drive.
I usually hit 1-10 west of Tallahassee and drive it to Jacksonville. That is a long, boring drive, usually about 4 hours for me. Lots of troopers, especially around Tallahassee.
Hope this helps.