It can be influenced a lot. If you have 2 top drivers in the team who has completely different driving styles, car preferences etc., than you have to make compromises in car development, in order to satisfy both of them. And that's why the top teams at some point during a season, have to make decision, who are they going to support as their lead driver. That means they develop the car with this driver's likings in mind and focus more on him during race weekends. So as you can see it makes the difference. Remember that Renault is not a top team yet and they have to find performance rapidly in order to catch up the front. And they can to it more easily if they are fully concentrated on one driver. Just look at 2008 BMW. They were catching up the front in the early stages of the championship but Nick struggled with the tires. So they decided to help him (because they wanted to treat the drivers equaly), which compromised their overall performance and development rate. I don't want anything like that to happen with Renault. So lets give Vitaly 2 or 3 races more and if he cannot adapt to F1, start looking for a better number 2 driver. Timo Glock is the first who springs up to my mind and hiring him wouldn't be a bad move since he struggles alot with this joke Virgin (level of frustration goes up
).
You're missing my point, which is that even in a car that is suited to Kubica, Heidfeld would probably be scoring better results than Petrov.
Also, how can you prove that Kubica and Heidfeld are more apart from each other, driver style and car preferences-wise, than say, Hamilton and Button, or Vettel and Webber? Maybe, just maybe Robert's and Nick's likings looked so much apart from each other because of BMW's incompetence to manage them, and not because their likings were actually impossible to reconcile at all?
How can you prove that helping Nick compromised BMW's performance and development rate in 2008? It's possible, but perhaps they just weren't able to fully understand the revolutionary design they came up with that year, hence couldn't develop it properly? How do you know they slipped back because of helping Nick and not because of some other reasons?


