Based on what? There's absolutely nothing to support that.
I find exactly the opposite, there´s nothing to back up your view.
There are 2 ways to look at this, what a "better teammate" is:
1) Looking only to the time these guys shared teams with Vettel and Fernando.
2) Looking at their full careers.
If you choose 1), Webber´s been better post 2009 than Felipe post 2010 on average, by a healthy margin.
And if you choose 2), you might lack some info to judge this way but I´ll help you: Massa peaked really high in the 2006-2009 stint, but further than these years, no matter where you want to look, be it early 2000´s or recent past, Webber´s been better the rest of the time. Webber´s average performance over his career has been superior.
Only way to hold your view is the "who´s better at both guys´ best". Massa peaked higher (still, I´d have loved to see 2003/2006 Webber in a proper top car). But that´s irrelevant, it didn´t happen while partnering FA, and if you want to average their careers, you have to do it properly, not selecting just a season/s that fit your agenda.
Edited by Skinnyguy, 27 June 2013 - 23:20.