It's not even close, and Ewan has won those TdF stages this year because of the unusually weak field, including the absence of Gaviria, who got injured and isn't there. Photo-finish with Groenwegen in Stage 11 and edging Viviani / Groenwegen by a wheel-length in stage 16
Ewan is a one-trick pony who is also inferior in strategy and style.
Because Gaviria has had a lot of luck against Groenewegen recently... Check De Panne if you want to see how they measure up against each other.