Well, that depends. The Chattooga River Trail is shorter and easier than the Bartram Trail (in my humble opinion) but if I remember correctly they are one in the same for a section along the river (so you could actually do both). I’d probably do the CRT first. The scenery is better and the terrain is easier. Plus you can always knock it off and get some miles on the Bartram Trail taken started in the process and do it later.