I have gone back and forth many times between the Toronto area and central Florida. My preferred route when towing is I-75 all the way to Detroit, then Ontario Hwys. 401 & 403 to home. Generally speaking the shortest way is I-95, I-26, I-77, I-79, I-90, Queen Elizabeth Way. It's about 100 km. (62 miles) shorter than the I-75 route. Even though it is a little longer on I-75 it takes about the same amount of time and I find it a much easier drive when towing. Just avoid rush hour at Atlanta and Cincinnati and you will be ok. The only real stretch that has any hills of significance is the 15 or so miles at the north end of Tennessee.