There are a couple of points that make me not so sure it's apples to apples when 2 guys are in the supposedly same car.
I'm wondering about the core buildup of the car... "settings", for lack of a better word, that are not adjustable, but more of the nature of the chassis. This chassis might for all I know be designed around the star driver. Every driver has different styles and techniques. The all need different cars to excel. If the car were built around Webber would he beat Vettel? Same question for a myriad of pairings - say, Alonso and Whoever teamed with him in Renault, or MS and Rubens, Hill and Prost at Williams, Hakkinen and Coulthard at McLaren, etc., if the tables were turned.
Also, even though a team says it lets their drivers race, One gets preferential treatment. Ron Dennis was famous for claiming his guys could race, but reading autobiographies and biographies I glean that in the top teams, the two cars are separated into two distinct separate teams within the team. The crews war against each other. Not much is shared. But there's a crucial difference between these two "teams": the team principal sides with one of them. That side always has more success because the boss' favouritism gets that side more attention in engineering and development stuff. Dennis rarely acknowledged Coulthard and always referred to that side of the garage as "them". The same thing happened to him at Williams. Dennis even publicly protested and appealed a penalty against Senna that benefitted his other driver, Prost!
Interesting questions you have raised. We could take them and apply them to the 3 drivers in the article and their teammates and see if any pattern emerges.
Every driver has different wishes true, but the mark of a great 'driver' as opposed to fast racer should be the ability to adapt and drive anything. Like the greatest musicians can play several instruments and make good music despite the medium, so a great driver should be relatively good in any car. There should be no excuse. Talent is generally divergent in nature and not convergent. How many true geniuses do we know who were one trick ponies? Micheangelo?
The 2007 McLaren was a car unknown to both drivers so thats a good sign of both drivers adapting and doing well. I cannot remember any car or car setup that has caused either driver Lewis or Alonso to lose significant performance relative to their teammate.
It is fairly obvious that most drivers have a comfort zone in which they will perform at their highest level. When the team is prepared to bend over backwards to accomodate that, and when it is to the detriment of the other driver, then there generally has to be favouritism. Either because the favoured driver is simply much better or because the team are more interested in social politics than competitiveness. This could have been the case in the second half of 2007, with Lewis preferred because Alonso turned against the team, however it could have been that Ron felt Lewis was faster (which he was). When we look at Seb, Alonso and Lewis in this regard we can safely say that Alonso and Seb appear to have been clearly favoured and the cars built for their comfort at the teammates detriment. Whereas Lewis has had much less instances and, indeed has had McLaren damage his chances by attempting to turn a duck into a swan.
So to cut a long story short, Lewis' technical advantage is the most adaptable, he maintains an edge over his teammates whether the car is neutral, setup for him or for his teammate. The edge has remained when he may have been favoured but also when the unfavoured driver with the team more focused on his teammate.
Alonso has only once been the less favoured driver, in 2007, and he lost. Apart from that he has always been the favoured driver, and as we all know the extremes to which his teammates have been disadvantaged and he wins all those. As far as I know he has never ever lost performance by not being able to adapt his technical adge
finally, Seb. He has never been the less favoured driver and has been better than his teammates. One could argue ofcourse that he and Webber were a lot closer in performance until Seb became the favoured driver. With the team focused on his comfort zone Webber no longer comes close, unlike the earlier years and ofcourse the period when he lost his trick. Sebs technical edge appears to be carrying speed and dealing with the oversteer, however it could be that unlike Lewis, Seb prefers (or requires) the extra downforce that appears through his 'trick' once oversteer is induced, to help tame the oversteer, whereas Lewis just relies on his ability.
So all 3 drivers are the fastest round corners, Lewis does not need teammates, favouritism or tricks. Alonso does not need tricks. Would Seb be as fast round the corner as the other 2 without the car built around his trick that helps tame the understeer? Or would he be as effective if the car was built for the comfort of his teammate?