I think it depends on what sort of tests you do. A resolution test might only verify that most modern filters are sufficiently flat.
When I've tested filters, I've found that in a flare-inducing situation (high contrast scene, light source in the frame), that, unsurprisingly, multicoated are better at suppressing flare and ghosting than single-coated are better than resin are better than uncoated glass. Even a cheap Vivitar VMC multicoated filter is pretty good as a filter.
Aside from the original question, there is a real difference among UV filters in how much UV they filter. Bob Atkins has a pretty good article on this on photo.net.
Other issues are mechanical--B+W and Heliopan have brass rings that don't bind easily, and Heliopan filters now come standard in slim rings, so they're better for wide lenses.
