Always use lens hood, UV filter is secondary

but without it, the front element of the lens is hard to keep clean and scratch-free over time, that will affect re-sell value. So get one, but not the most expensive one. I never saw a solid proof shows the real world difference on image quality between OK UV filter or best UV filter. Hoya multicoated or above should be good enough.Yes there are two reflecting surfaces; but inside the lens, there are probably already 20 reflective surfaces, I don't care add 2 more.