There are only 3 important considerations when choosing a CB antenna:
The longer the antenna, the better the range. There are always trade-offs between performance, aesthetics, and height restrictions, but just remember that the length of the antenna will have a direct affect on the range of your CB.
Fiberglass vehicles must use a “no-ground-plane” antenna. This is a special antenna designed for fiberglass RVs and boats. These vehicles need a special antenna since the body is not made of steel. You can find “no-ground-plane” antennas at places that sell RV and boating accessories.
If you need weather reception, make sure the antenna is compatible with the weather band. All center-loaded antennas and all fiberglass antennas are compatible with the weather band. But if you choose a base-loaded antenna, make sure the package says that it is compatible with weather.
Beyond that, it is just a matter of choosing a mounting method that works best for you. There are a large variety of mounting options available for CB antennas.