You would be better off investing in a permanent coating and window tint IMO
I reckon there'd be no harm in doing both?.
The cover has other advantages, and also some disadvantages also. I would say a cover will possess a higher degree of UV blockage than any protectant in a bottle that one could ever place on a vehicle.
It "hides" a vehicle from prying eyes, offers some abrasion resistance from flying objects to an extent.
Such as the Covercraft NOAH, it may ease time spent cleaning a vehicle, or when it does need cleaning, the processes are easier.
The downsides are of course the installation and the removal of the cover when you need to use the vehicle. If that's on, or almost on a daily basis, the work will get somewhat aggravating over time.
If you need the use of the vehicle immediately after a rainstorm, this can be a problem if the cover is still wet, or damp. The problem will then be, where, and how do you store the cover so it will fully dry, and not have molds-mildews develop?
I've been very happy with my Covercraft NOAH, no regrets in buying it.
Since they are form fitted, and custom sewn for every vehicle, their appearance will mimic the vehicle underneath. Still though, so many midsize, and small cars look similar today, a passer by would not be able to easily identify if the vehicle underneath is a Lexus, a BMW, a Hyundai, etc.
I agree fully about insuring that you exactly know what the cover's features are for your particular vehicle. Any things like Custom Ground Effects, or as mentioned a Shark Fin Antenna, etc, do insure that cover includes such.
Non-removable Whip Antennas will most likely mean the user placing a hole and grommet on the cover where required. If needed, insure that the cover comes with such.
Because if not, you will be sending that cover back for alterations-modifications, and it will more than likely be on your dime.
The Gust Guards, and Security Cable are IMO must haves. Mark