If you consider the I-40 route, there is also an alternative to consider when you get to Little Rock, AR. Rather than taking I-40 from Little Rock to Memphis, and then the madness of the I-40/1-55 merger in West Memphis and crossing the Mississippi, consider this:
I-530 south from Little Rock to Pine Bluff and pick up US 65 south to US 82 and the crossing of the Mississippi to Greenville MS, and then take US 82 all the way across MS. Good 4-lane road and you miss all of the truck traffic on I-40 east of Little Rock as well as trying to get through Memphis. US 82 will take you all the way to Tuscaloosa AL where you can pick up I-20 to B'ham and I-459 around to pick up I-20 again on in to Atlanta.