If you really need a filter for a certain kind of pictures, take the best your money can buy. A tipicall example is polarizer: the better it is, the easier you'll sell it when you'll need something else, and no falloff for your picture's quality.
If it is not strictly necessary, why to add something unnecessary and that lowers quality? I'd rather spend some more money in MC lenses, instead. By the way, manufacturers best regarded for their multicoatings (i.e. Pentax to name one only) never let out filters with such coatings...