IF you can swing it, get an enclosed trailer. I had a tilt bed trailer for years and it worked great(one machine)but after a few winters of salty road sludge, my quad was really starting to suffer = rust. That’s when I started looking at enclosed trailers.
I guess it all depends on how you use your quads though. Warm weather is no big deal but I mostly use my quad for icefishing so it sees a lot of trailer time on the road. Mine is 6′? by 10′ and I can fit my quad, ramps , portable and all my ice gear inside plus lock it up if need be. I don’t recall the price right off hand but it was in the aluminum snowmobile trailer price range. I would do it again in a heartbeat if need be.