I don't think anyone is favorites really. United and City are the obvious two, but Chelsea and Liverpool with no european football and excellent managers can definitely put up a challenge, and Arsenal have a good side even if they always feck up somewhere. In terms of starting 11's, don't think there is anything between United, City, Chelsea and Arsenal. All have a few weaknesses, all have their strengths, all have sufficient depth for their competitions.
City again are being incredibly overrated as they were the last 2 years where I said both times they won't come close to the title when everyone said they'd walk it, but there you go. A few top but injury prone attackers and suddenly they have the best side. With hart in net, a pretty awful defence, and a very average midfield, it's what will undo them. Gundogan is a good signing, but he has had plenty of injury issues so it's no guarantee he will be fit enough to make a big impact in the premier league. Also, who gives a feck if they sign Sane, Nolito, Gabriel Jesus on top of Sterling, Navas, De Bruyne, Silva, Aguero, etc... I'm not sure they've actually strengthened their starting 11 with any of those. Good potential with Sane of course but he's far from the finished product. Their attack was never their problem and I'm sure they'll score a lot. The problem was their back 4 which they haven't strengthened, while with Pep especially there will undoubtedly be teething issues through his style of play and the back 5 not suiting it in the slightest (just look at their friendly with arsenal... shambolic at the back would be putting it kindly). Also on their actual quality players... They are all injury prone. Aguero can never be relied upon to last a full season, and his back up is Bony who is shit. Silva has declined a lot, and he's very injury prone as well. Kompany hasn't had a good season since 11/12, but he is injured 90% of the time anyway. De bruyne is class though and not normally injury prone, but even he got a big injury last year.
Chelsea walked to the title with Mourinho a couple of seasons ago, and have Hazard who can be the best in the league at his best. Kante a great signing in midfield, especially alongside Matic and Fabregas. Willian a very good player too. Weakness for them is if any of their strikers can get consistency, and their back 4 which is a bit shit.
Arsenal have 2 world class players with Sanchez and Ozil, and some very good players in midfield like Cazorla and Xhaka. Obviously missing a top striker but Giroud is usually good for 20 goals until his usual drought. Missing any depth in defence though, and plenty of injury prone players back there. Signing Mustafi and Lacazette like they are trying though would improve them loads.
Liverpool has improved a lot under Klopp, even if their consistency isn't there. Capable of having great performances, and capable of throwing away easy points. They won't have the consistency to win the league, but then again, have only the league to worry about to they could be a dark horse. Think they'll get top 4 though.
Spurs will decline from last year I think. Pochettino and Spurs fans seem to be thinking that everyone will just carry on from last season and improve linearly because they are generally pretty young... But it doesn't work like that ever. You always need to change things up, and all they did was sign a depth player in defensive mid and up top. Will be interesting to see how they deal with champions league now as well, as even though they had the Europa league before, they didn't care as much about it. Now they have 2 competitions they will give their all for. A lot different.
United has obviously had the best window, and bought exactly the players we needed to suit our squad. Mourinho reportedly wants one more center back, and that would be the icing on the cake. Our success for the season rests on if we drop Rooney or not. If we continue to shoe horn him at the #10 position at the expense of getting the best out of Ibra, Pogba and Mkhitaryan, then we won't win the title. Simple as that IMO. If we drop him, change to a 4-3-3, and get the best out of our new signings, we'll see some great stuff and be in for a great season I think.