We took Amtrak's Auto Train right after 9/11 (we were too scared to fly).
I was pleasantly surprised by the spaciousness of the cars! We had plenty of room to relax. We, too, rode coach due to the expense and it wasn't bad at all. The bulk of the trip was at night, so we slept through it. By the time we woke up, the train was slowing down & close to Sanford, FL.
The "cons" of taking the train were minimal. My only complaints were the rocking of the train, and the frequent slowing for other trains to pass (seems other trains have the right-of-way on the tracks). Other than those two things, I have nothing bad to say.
The following year we drove from Philly to Orlando and I have to say it was brutal. My husband did 90% of the driving and he looked like a zombie by the time we reached Georgia. It was a little scary for me, too, because I sat with my eyes glued to him to make sure he didn't fall asleep. The ride home was even worse because we were depressed about leaving the warmth of FL and heading into the cold of Philly. I don't think I want to drive again.
So, between the train & driving, I'd pick the train. Let someone else do the driving while you relax!