A covered RV port is great if you have the space. Have had experience with an ADCO cover for the last three years.
It is not designed to be waterproof. It is designed to breathe. Plastic is not, will trap moisture and promote mildew.
It will not scratch or cause burn marks on your TT. The material it is made from is soft, unlike plastic sheets and tarps.
Installed correctly, it will last at least three years as mine has no holes or tears. Yes, I have seen brand new TT's covered with brand new covers that were in shreds at the storage yard - but I also see how obviously bad of a job was done installing the cover - nothing covering the gutter spouts or other protrusions.
It will keep inside temps lower during the summer months - has a white reflective top.
It will help keep your TT clean. Sure, you will still see dirt and streaks, but these wash right off if you have waxed it.
It is not "a pain" to put on or take off. As stated, read and follow the dirctions and your life will be simpler.
Sure your TT is designed to be outdoors, but this doesn't mean it's bullet proof. It takes effort to maintain a new like appearance. Comparing mine to those left uncovered is all the motivation I need to keep mine covered.