After re-reading this thread it really got me thinking about what happens to our transparencies when it's time to print. Almost all of us are scanning these E-6 films now and printing either lightjet, chromira, lambda, inkjet.. etc. So any color cast or saturation differences between these films can easily be corrected for in P****S*** before printing. I could make Provia look like Velvia, or easily correct the blue cast of provia 400. So to me the choice is easy, I'm shooting Provia for its slightly lower contrast and I'll worry about everything else later.
Tinkering in a computer is no match for a properly-filtered piece of film. A lot can be done there, but even then, it is best to start with an ideal piece of film. Filtering properly balances the exposure on all three layers, which is the only way to get truly accurate color balance.
"Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."
Provia's great. Some people say it ain't saturated, you just have to know how to use it ;-).
Velvia, IMO, is great for certain subjects only. Personally, I'm more of a "represent it as it really is" kinda guy, at least 90% of the time. The other 10%, I like to go hog-wild, so I use Velvia 50 .
Astia is great too, great for skintones, especially in the studio, where you can control your contrast and lighting easier than in the field.
Negs are for people who don't know how to properly meter their shots . Just kiddin, I still shoot Portra, sometimes...