I can't give you a specific brand recommendation but will share some experience. I like covers but many don't. Both covers I have had were in the $500 range for 30+ ft 5th wheels and worked well but were flimsy. Presumably this was due to using material that is both light and breathable. I would love to find a sturdy one that would last awhile. If you live in a windy wide open area, you will be lucky to get two years out of one. Wind may also cause it to rub which also can scratch your finish in addition to wearing/tearing the cover. However it is great for keeping the sun and tree gunk, etc. off of it. They are a pain to put on/take off although a small trailer would be much easier. I have heard that custom ones that fit your trailer properly are better but I've just had generic ones that tended to be a little sloppy in fit. My current cover is one year old and in a sheltered area but already has some side rips from removing or adjusting it. I try to catch them while small and slap gorilla tape on both sides of the tear. These repairs seem to be at least as strong as the cover material. You still need to wash the rig when you unwrap it but it is easy compared to scrubbing 6 months of winter and oak tree scunge if left uncovered.
I feel they are flawed but worthwhile to protect your investment but I suspect the majority will disagree. Everyone's circumstances are different. "It ain't the job, it's the decisions."
2015 Crossroads Cruiser Aire CAF27RL, 2018 F250 diesel crewcab SRW 4WD short bed, Trailer Saver hitch with Reese adapter on Ford OEM underbed 5th wheel connector.