I think deciding whether to filter, and which filter to use, would depend on the scene.
At the risk of giving examples of something I know nothing about, here are some photos on Velvia 50 with no filter.
These were taken in 2010 at Whiteface Mountain in the Adirondacks, New York. This is the first time I used Velvia.
(Sears KS-2 (Ricoh XR-7) 35mm camera, pro-shop consumer-level scans; I de-rezed and re-sized in The GIMP. Also, I just take snapshots, so obviously my composition and exposure are not great.)
The first is the trail leading up Whiteface Mountain, I think it's okay without a filter, though it could stand a little warming.
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The second is looking back down the trail, I think a skylight filter may have helped (also note the mid-frame light leak).
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On the third, although a bit contrasty, I'm not sure if a filter would have been an improvement.
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