Brownsville looks a pretty nice neck of the woods! Lucky you.
The big difference between an A and a C is storage. From a 1 ton Van Chassis to an F53 (small gas Class A or to a Diesel Pusher. An A will get you a lot more outside storage plus you sit up higher so you get a better view of your surroundings. We have gone through two Cs and we are on our second A. Both of our As have been F53 gassers. Our first gave us 14 years of great service. We have only had our latest A for just over a month now.
If you are planning to be traveling for 6 months I would definitely go A. Make and model are important but I believe FLOOR PLAN is the most important. Most coaches are built on Ford's F53s so drive train isn't that important. You can check different model forums to see what owners find good and bad about their rigs. Are you planning on towing a vehicle? We would not be without our Jeep for running around.
If this will be your first outing for 6 months it will also give you a bit of an idea of what full time will be like. Obviously, we love our lifestyle but it is not for everyone. You get to know your partner real well. Prior to retirement most people only spend a few hours a day with their spouse. Full timing means you are together 24/7/365 in around 300 to 400 sqft. One learns the meaning of compromise real quick!

We have met a number of people that have given up after about 6 months. Some made it a year. The vast majority go back to a stick and brick. We are fortunate in that our interests are very similar. We like history and there are so many interesting places to visit. We tend to stay away from big cities as most seem to be alike. We like nice scenery. We do some hiking but age is creeping up on us so no more vigorous long walks anymore. We have e bikes that help us get to some of those distant places (where they are allowed). We have our Jeep that lets us get to some of the less visited Ghost Towns, old mine works etc. There are exceptions to visiting some big cities. There are those that are worth seeing. San Fran, LA, St. Louis, Independence/Kansas, Dodge, New Orleans, Memphis, Old Quebec City, DC, and a number of others. We have our 2 year old Miniature poodle that keeps us on our toes. "I" tend to travel on my stomach. My wife does a good job of holding me back to keep my wait somewhat in check. It seems every area has a food that is their specialty and I gotta try em all. I love BBQ and every state has a different flavor. I love sea food so visiting any coast is great for me.
One of the big drawbacks of full timing is missing good friends and family. We spend our winters south so it will be at least 6 months before we return to our home base territory. We try to visit everyone we can and maybe stick around for a moth or two but then the urge to travel hits again and we are off. We will try to get back again before heading south again but sometimes it just doesn't happen.
Anyway, we were kind of disappointed when visiting the Alamo but seeing San Antonio's River Walk made up for it. Oh and when in Texas, you gotta stop at Luckenbach for a long neck....just because!
I'm sure you are going to love your journey.
Darrell