If you're gonna go Velvia go Velvia 50, I don't find anything 'wow' about Velva 100 or 100F.
I'm gonna chuck my vote in for E100VS for the 'wow' factor, otherwise go Astia or E100G.
E100VS doesn't go ridiculously blue in cold light unfiltered.
Mamiya C lenses look fantastic in colour.
My first home E-6 test (Kit E-6, as opposed to all my Xtol and Rodinal "E-6" and DIY mixed "E-6") stuff with 180mm Sekor C wide open.
Unfiltered in late afternoon very heavy overcast cold light.
DIY E-6 Test Roll by athiril, on Flickr