I think Mertesacker's reputation is much larger than his talents. He was horrid this past season, sluggish, slower than ever and terrible distributing the ball. I estimate that more than a dozen goals can be attributed to unforced mistakes by him. At this point, Friedrich is so much better than Mertesacker it's not even funny.
Wenger should be fired, to be quite honest. He turned Arsenal into a club that doesn't really contend for the title any more. Installed a losing mentality. That's great for him - coaching without the pressure of having to win! It's terrible for the club though.
I'm also unimpressed with Chelsea's off-season. Mata was the type of acquisition they needed but I'm not sure it was enough. I think they still lack creativity, offensive explosiveness. If Modric failed, they should have gone after someone else. Guys with the talent to create opportunities out of nothing. As of now, there are too many strikers and too many mediocre/ageing players as wingers and CMs. In fact, I think AVB had more offensive talent in Porto last season than in Chelsea this season (starting XI) only, which is kind of sad considering the difference in resources. Mata helps, but they needed more. Hopefully the spaniard stays healthy.
Meireles is a nice player, but he has stamina issues when asked to do that box-to-box job (the one he has done for almost his entire career). AVB should have paid for Moutinho - a world-class version of Meireles.
Liverpool... I like their team, but I question the decision to spend more than 100 millions in the likes of Carroll, Downing, Adam and Henderson. I think that Dalglish is still a great a coach, very astute tactically and as a man manager, but he's too old fashioned when it comes to personnel decisions. Those guys are good players but like any other Brit, their price is grossly inflated. And Coates is a nice young prospect, but he's not used to defend high-up the pitch like European teams do and he'll struggle a bit as his acceleration, while better than one would expect, isn't top notch. But he had a great Copa America...
Just imagine how good Liverpool could be if they had spent the money in, I don't know, Pastore, Falcao and Lucho Gonzalez. Or they could keep one of CMs they sold and acquire a winger like Hazard. Plus a really good central-defender: if they wanted a young south-american, Rafael Tolói or Mário Fernandes, who have higher potential than Coates and are more suited for the European game. Same money spent and they'd have a much more talented team.
Those 3 teams could have done better. Therefore the Manchester teams ought to be considered favourites. Just slightly though, I don't think the situation is really comparable to Spain or Scotland.