My conclusion is based on far more than just the race wins alone.
In 2010, Mark Webber drove the RB6, which was the fastest car throughout the season by a large margin over Ferrari and Red Bull. Webber did not have the reliability issues Vettel did. Despite that, he was beaten in the championship by both Vettel, who drove a much more unreliable car, and Alonso, who drove a much slower car.
In 2008, Felipe Massa drove the F2008. It was the fastest car throughout the year in the dry, but only slightly faster than the McLaren. The Ferrari was also slow in the wet and had bad reliability. Massa finished only one point behind Hamilton in almost equal cars. He also dominated Raikkonen in the same car.
Isn’t that enough to prove that an in prime Massa is better than an in prime Webber?