"I repeat: we are building the team around Sebastian," Horner told Auto Bild. "Sebastian has a long career ahead of him and hopefully he will spend it with us. Mark is in the autumn of his career. He wants to retire while he's at the top, not when he's past his peak like some other drivers."
Comments extracted from this article here http://en.espnf1.com/redbull/motorsport ... MP=OTC-RSS
I would like to make it clear, though, that Horner is specifically referring to future seasons (i.e. 2011 onwards) - for the moment, there are no indications that Red Bull are favouring Vettel over Webber at the moment. In fact, in theory, it should be Webber who is favoured, as he is the leading contender in the drivers championship, although whether that is borne out in practise is another debate entirely...
Although this is not surprising, given that the management of Red Bull, in particular individuals like Mateschitz and Marko, have stated their preference for Vettel, it is still disappointing in some ways. Alonso, as to be expected, has installed himself as an undisputed No. 1 driver at Ferrari, Renault have traditionally run a No. 1 and No. 2 driver system, and now it seems that Red Bull are going to do the same thing. Only Mclaren, it seems, intend on treating both drivers evenly out of the leading teams.
I have to admit that whilst the practise is fairly widespread, I'm not always that keen on seeing it being implemented. Being made a subservient second driver often ruins the career of many a promising driver as they are undermined from within the team. We saw that Rubens was steamrollered by Schumacher at Ferrari, how Alonso was the favoured one at Renault under Flavio's rule (and how Trulli was thrown out of the team in 2004, even though, up until that point, he was ahead of Alonso in the WDC).