I think Webber was thoroughly shafted in favour of Vettel in 2010. Remember some of the stupid things Vettel did that year, including taking himself out and nearly Mark as well. The way the team reacted with sympathy when he got back to the pits demonstrated clearly where their preferences lie. If it had been the other way around Mark would not have been treated the same. In fact he probably would have been history. They always do a bit more for Vettel than they do for Webber, and that goes down well with the RB hierarchy.
There's a lot goes on behind the scenes that outsiders don't get to hear about, and I think Mark Webber has done very well to hang in there, because he's at a disadvantage. They manage to hide it very well, but in a sense Helmut Marco has now stepped out of line revealing the true state of affairs. I bet Christian wasn't best pleased when he found out what was said. He's done a fine job of masking the favoured position of Vettel. He'll still deny it of course. I can't wait to see his body language when he's asked about it on camera, as he surely will be.
Most of the time Webber hasn't quite got the edge that Vettel has, but he's not far off. His drives around places like Monaco show that very clearly. He's had the occasional off-day, but who hasn't? Only Alonso this year, and even he won't be able to keep that up forever. From Webber's point of view though, he's got to overcome the disadvantage of being treated as the number two, as well as beating all the other drivers. He could still yet come through, but it's tough. As for signing the contract with RBR, definitely yes. He's in the best team he could be and they've got the best team mate they could have for Vettel. Whoever takes Webbers place will probably come via Torro Rosso.
I have a different perspective on this.
I found the 2010 Turkey incident very telling in terms of Webber's attitude. Vettel was told he could pass Webber and Webber was told to let Vettel through. The order was given on the basis that Webber was in fuel-saving mode and Vettel wasn't and if Vettel remained behind Webber in that situation he was vulnerable to the McLarens. Now whether there is agreement that that was actually the case, both teammates were told what was to happen by the team. Vettel then went to execute the overtake assuming Webber would let him through but Webber didn't. Of the two it was only Webber who could have avoided the accident in that situation without serious compromise by backing out a bit because Vettel was committed. Instead of doing that he preferred to fight and an accident ensued that cost the team in total serious points. At best it was bad communication by the team in not making it clear to either Vettel that his teammate wasn't going to put up a fight or in not making it clear to Webber that he was to actually let Vettel through; at worst it was Webber being bloody-minded and stubborn.
However, what really highlighted Webber's attitude was the way he managed it afterward. Instead of saying that it was a badly handled situation and something the team and drivers would learn from, he chose to paint himself as the victim and be spiteful about the whole thing. Even if what he was saying was the truth it was bad behaviour to effectively slander his own team in public. However the fact that it wasn't the truth made it extremely poor form and just highlighted a massive chip on his shoulder.
The team being sympathetic to Vettel when he returned to the pits is not telling of anything. Of course they're going to be sympathetic when their driver's race had ended regardless of the circumstances. Even when a driver has done something truly idiotic I've never seen a team abuse them upon return to the pits.
I don't believe that any preference for Vettel compromised Webber at all in 2010. Red Bull allowed their drivers to race right up until the very end while both were in the championship hunt. They never made Webber play a supporting role of any sort to his teammate. As an aside it's interesting to me as well that in Brazil Webber was implying that the team should have made Vettel pull over for him because he was their best chance for the championship despite the fact that both drivers were still in with a genuine chance. Yet when the shoe is on the other foot, and he's actually mathematically out of the world championship, he doesn't play the team game properly at all. Talk about hypocrisy.
Subsequent to 2010 and 2011 because Webber was absolutely nowhere near Vettel that year, I don't see any problem with Red Bull having a genuine preference towards Vettel. He had two world championships to Webber's none and he had showed that he could sustain his performance over the season, overcome the adversity of mechanical failures and that given an opportunity will capitalise every single time where Webber simply doesn't have that consistency nor can he handle that level of pressure. To paraphrase what Irvine said about Schumacher, "of course the team preferenced him - he was the better driver by quite a bit!" However, while Red Bull might preference Vettel in terms of the direction of car development (and I'm still not sure that is the case - I rather think Newey directs a build of the car he thinks is the best and it just suits Vettel more), I've still never seen them actively compromise Webber in the process. They've never had him pull over for his teammate before he was mathematically out of the championship and even then only when it was absolutely crucial. There's no strategic compromise in either qualifying or the race.
They've also maintained a very professional attitude about him despite his own behaviour. When he said, "not bad for a number 2 driver" at Silverstone in 2010 they didn't react. And when he didn't even come close to being a team player and actually compromised his teammate in Brazil 2012 they didn't come out and say anything negative at all.