Hey, been out of pocket all day, but don't have tons to add to what was already posted. Yes, March in the Panhandle can be marvelous or it can be brutal. If we don't get rain, you could have some real bad sandstorms then.
As I said in the linked thread though, the canyon really modifies the weather. Protects you from the wind, etc. Beyond that, prepare for anything.
Spring break is a busy time at PD Canyon, so book a site early if you can. I'm not really a camping person, but I don't think there are very many true "primitive" camping sites, as in hike in-hike out. I do know there are sites with camping pads next to where you park your car.
Caprock Canyons does have hike-in primitive sites, as I recall.
As far as picking between the two:
Palo Duro is more developed. It is also close to a major city, so you're going to have more day visitors in and out. Probably more campers and fifth wheels. And since you are in a canyon, the scenery is more spectacular and the bottom of the canyon more protected from the wind.
Caprock Canyons is the same type of terrain, just further down the creek so it is more open country. Bluffs on one side, rolling terrain on the other as opposed to bluffs on both sides.
CC will likely be much less crowded, and it's going to be slightly less of a drive. Still a beautiful park if you like the caprock country. And it has the Texas State Buffalo Herd.
The down side is that CC is miles from a town of any size. Quitaque has a Allsups, and that's pretty much it. So no museums, restaurants, etc. as with PD Canyon. No easy resupply of essentials.
The rails to trails is interesting, and it does have some primitive camping off of it. The downside is that most of it is away from the bluffs of the caprock, and mostly down in the rolling farm and ranch land. Maybe an overnight camping place, I wouldn't consider it for a week. Google "Clarity Tunnel" for the tunnel on the trail. It was the last active railroad tunnel in Texas when it closed down 20-30 years ago.
Post any specific questions or pm me for more info.
Ironically, we may be in San Antonio in march. Daughter has training at Randolph, and we're probably going to be headed south about the time you head north.
[This message has been edited by CanyonAg77 (edited 1/8/2013 9:39p).]