After making hundreds of profiles both ways (I have a Spectrolino with removeable filters) I'm now making all my profiles with the UV filter attached. There is very little difference between them, but the difference I do see is that I get slighty more neutrality along the entire gray ramp with the UV than without. The difference is very very small, but for my money, trying for that last little bit, it's worth it.
I also find that for profiling canvas or any very textured media, nothing works better than the Polarizing filter, which also cuts UV.