Finishing wise I'd say they're really close, which really shows the value of Carmina.
Fit and feel wise, Vass is superior, they're lightweight and almost feel like wearing slippers...it was uncanny when I first tried mine on.
Pretty much no break in period, whereas my Carminas all took a couple weeks of wear to be comfortable.
My humble opinion and experience thus far is that Vass fit like gloves and the fit is definitely much better than Carmina. The heel shape on Vass grips much better.
Also agree that there's pretty much no break in period whereas I know that I will expect pain for the 1st few weeks on my Carminas before they are comfortable.
Construction wise - Vass is handwelted - which is supposedly superior to Carmina's Goodyear
The other one is that Vass uses leather toe puff and heel counter stiffeners vs plastic on Carminas
Just my humble opinion and YMMV