Spanno,
Between the two campsites I would say that Bush Mountain is better. The sunsets from there are spectacular to say the least. Tejas is better if your seeking seclusion and lots of trees.
As far as elevation gain is concerned, you're going to hit the majority of your gain from Pine Springs up to the Pine Top intersection (roughly 2000 feet in total) regardless of which campsite you prefer. Going to Tejas, you'll flatten out shortly after Pine Top and actually drop about 500 feet before you get there. Going to Bush Mountain, you'll climb an additional 500 feet or so after Pine Top and you'll be camping at the base of the second highest peak in the state. I was climbing with a full pack which included three day's worth of water so needless to say I was pretty worn out by the time I got to Bush Mountain, but again it was worth it.
All the trails I encountered are easy to follow but they are a bit rocky so make sure you have shoes with good soles. I had trail runners and wished from time to time that I had something a bit more solid. Trekking poles will certainly help as well.
I too live in the DFW area and the drive took roughly eleven hours. I preferred to leave early in the morning so I could get there in one day. I also got there early enough so I could get my backcountry permit that afternoon and hit the trail first thing the next day. If you want to stop at a motel, Van Horn is about the closest place you'll find. It'll leave you about fifty miles to get to the park.
I don't have any knowledge of the area past the Blue Ridge trail as that's where I turned towards Tejas, but I would suggest that you don't miss the hike up Guadalupe Peak. It's an excellent dayhike with an awsome view. The Smith Spring Trail is also another one not to be missed.
To give you a visual reference, here's a link to some photos I took:
