Wed 12-Dec-12 12:48 AM | edited Wed 12-Dec-12 12:48 AM by JosephK
I cannot speak about the 28-300mm, but with my 70-200mm II I can see the difference with and without the UV filter I have. Granted the filter is mid-quality at best. Any extra glass added to the front of a lens will degrade the image, some more than others. If the filter is not providing a photographic purpose, you probably should be questioning its use.
If you are not in a harsh environment (and most people are not) then the lens hood will give you all the protection most people need.