Provia is OK for skin tones as opposed to Velvia, which is not.
I would angle for Portra 160 for skin tones in lieu of Provia if it was really important. Provia is a 'watered down' Velvia with reduced contrast and muted primaries, and trumps Velvia with very good shadow detail. It's commonly used for early morning and evening shots for additional speed over Velvia. Many photographers have their own opinion of it: I don't really like it but do use it in my Zero Image pinhole and especially for star trails, letting reciprocity take hold to give the heavens an other-worldly purple hue! :p
As for what happens with slides, my Velvia 50 trannies go to high resolution drum scan, despotting, colourimetrics, proofing then printing, matting and framing — and put up on the wall for all to see (not the Flickr wall or anything else: I don't post anything online that is my property). Those that are not printed are stored with many, many others still in archival sleeves.