Man Utd are stronger than last season for sure in attack. Plus Vidic is back. I just think Man City showed more quality last season, and showed their lack of experience as a unit and as a title-challenging team when they began to mess it up. After winning the title and gelling together better, I reckon Man City have gained more than Man Utd and are still significantly stronger (plus have possibly the best squad in Europe after Real).
It's likely that guys saying RVP isn't much of a loss are being bitter (why shouldn't we be bitter though...). He is a huge loss. On paper though, we have replaced him with Podolski and Giroud so things aren't too bleak. He carried us last season, in both a creative sense and a goal socring sense. A squad wins you the title, and Giroud and Podolski as strikers are together in all likeliness better options as goalscorers. Cazorla is finally a Fabregas replacement as well (though not as good), so should bring the creativity back as well. So in those senses he isn't a huge loss to the squad I don't think. He was 29 as well, and a complete crock, so who knows. Another season playing every game would've tired him out and possibly injured him too, so really it's not as big as losing Fabregas, and we survived losing him, Nasri and Clichy. So we'll do it again for sure.
In another sense though, RVP is the biggest loss yet. We've just lost our club captain and it has finally been officially confirmed that we are nothing more than a selling clubs. It hugely unsettles the club (Walcott and Song are surely gone now too). RVP was a true leader in every sense last season, more so than Fabregas and more so than Vermaelen will be.
Overall though, we will be fine, and I'm sure we have a chance at 3rd still as the money will be reinvested into two new players. Man Utd are once again significantly stronger than us though squad wise.