Good for you for starting your research early!
A lot of your answer depends on how big/how many dogs, and what you are comfortable driving/towing. A class C motorhome has a lot of advantages: you will have a generator, you don't have to hitch/unhitch anything, and it's easy to find spots for the dogs to ride in their crates. The disadvantages are every time you need to move your vehicle, you have to move this big monstrosity, and unless you go to a really big class C you won't have much space. Our first RV experience was a little C like you described. It got really old having no place to sit besides the bed, especially to eat. Then we moved into an older Class A. Plenty of space, crates rode in the dinette while we were in motion, and sat on the floor in the front when we were parked. However, I really hated driving it, and that, coupled with its advanced age and mechanical problems led us to downsize. We are now in a pickup/travel trailer, and are actually in the process of shopping for a somewhat larger trailer. I have corgis, and even with three small dogs it gets very cramped, very quickly. I am currently leaning toward a bunkhouse model with an eye toward converting the bunks to a dog space. A toyhauler also works really well..
The next few trials you attend, look at the grounds from an RV perspective. Where do the RV's park? Ringside? Near rings but on site? Off-site and driving in for the day? How are those RV's hooked up? Do they have water, power, and sewer? Just power? Or are they dry camping (just your generator/batteries/water tanks)
I compete in herding, obedience, and agility, so I see a lot of different venues. Our favorite herding facility does not allow RVs on site, so everyone camps at a rec area less than 5 miles away. Driving to the site is easy for me, unhitch the pickup and go. Less fun for those in the big diesel pushers, they have to either tow a car behind or hitch a ride! Most obedience trials are at either schools or fairgrounds. Schools tend to be a dry-camping experience, but at least you are on site. Fairgrounds usually but not always mean at least electricity and frequently water too, but you might be a ways from your rings. Most of the agility trials I attend are in city parks. Can't camp overnight, so folks use nearby RV campgrounds and park in the day-use parking lots. Knowing where you will be staying most of the time will affect your decision not only for type of RV, but how big your water tanks, generator, etc need to be!
