A warning about Dallas as well is they've went to toll road with camera enforcement. When you are trying to navigate a new city, the signage sneaks up on you too. I don't think it affects the route given to you to get to I-40 but something worth being aware of.
I've driven across TX on I-40 and I-10 and it's a long painful drive regardless. I'd go with whichever is shorter (I think it's I-40). And you have to pick your poison on Houston vs. Dallas with a trailer. If you leave Pensacola on 17th, you can catch them on a weekend and not deal with as much traffic.
