I used to use nothing but Velvia.
But now I find myself using 160 VC more and more, when I use color. Part of the reason is the palette, part is the wickedly wider contrast you get from c41 films, and part of it is the fact that I have a rental darkroom with a C paper developer machine available. It's much easier than BW, once you get the filter pack right. ANd I have not seen a cibachrome machine in 20 years. Also, it seems that the Lighjet process is as easy with c41 as it is with e6. And I have a feeling that I will be doing lightjest work long before I will be doing digital BW work.
PS for BW:
8x10: HP5 in ABC
4x5: Bergger and HP5 in PMK
6x17/35mm: HP5 in PMK