We had an Expedition brand cover for our last trailer. If was the cheapest we could find - nonwoven fabric with really cheap zippers. It fit pretty well, but was completely shot after 2-1/2 seasons.
We replaced with a CalMark cover that was much more expensive, but since it was semi-custom made in the USA to our trailer's measurements from woven Sunbrella fabric made in the USA with real heavy duty zippers, straps, and hardware, it held up great for over three years until we traded in the trailer.
We have purchased another CalMark for the new trailer.
With the ready made covers, I think the most important thing how they fit your particular trailer, and how well you secure them. Take some exact measurements of your trailer - don't use the manufacturers spec sheet - then read the cover manufactures catalogs carefully to see which ones are the best fit for your unit. If the cover is too small, you will stretch it too much getting it on - if it is too big, it is difficult to properly secure all the excess fabric.
Bill & Kate with Zeke (parti-poodle) & Bailey (std poodle)
Stone Harbor, New Jersey
2014 Forest River Wildcat 272RLX Fifth Wheel
2018 F-250 4x4 Crew Cab 6.2L Gasser