Gauge of the metal will vary by the type of metal and what it is combined with. Axles will vary on the size of the trailer. A two horse bumper pull will have a totally different axle assembly than a 14" LQ 4H Gooseneck. Just make sure you have enough axle capacity for the weight of your loaded trailer Suspension will almost always be a Torsion Bar type of suspension. Unless you get a really old trailer. Temperature Regulation is how many windows you can open. A stock trailer with open sides will give you the most ventilation and probably help with summer heat in the south. For my part of the world, I also need to be able to close up the trailer to stop wind in the winter when it's cold. For me Large Drop down windows on both side ( curb and street) allow me to control how much ventilation the horses get and control the temp inside the trailer. Roof supports will only matter if you plan on putting stuff up on the roof. Generators, hay, water tanks, storage pods etc will all require different support members depending on how much weight you want to put up there. Just about any roof structure should support the occasional snow load or wind. So if you are not putting anything on the roof to store. No problem Brakes, Most modern horse trailers have electric brakes. The larger LQ gooseneck some times come with Electric over Hydraulic brakes. But they are not very common and rarely seen in smaller trailers. You really need to give us more info about what you are considering in order to get better answers. | 
Trailer buying tips help
