I've managed all 4 of these
I found managing Dortmund very easy and probably the easiest of the 4 clubs you highlighted they should be predicted top 3 easily. young squad with plenty of potential and they are the defending champions, they are on the up. A lot of other big german teams (Schalke, Wolfsburg) are awful so its a fight between you and Bayern really, if you get the tactis right. I've always Dortmund come up with good regens too. Kagawa always wants to leave and he is good, but he can be replaced so its not too big of an issue.
Atletico have a pretty poor squad considering thier media prediction, it should be 4th really. Falcao is obviously world class, but there are too many average squad players and not enough superstars. Dont really have great finances either but are moving to a new stadium with 70,000 seats. Need a new GK if you cant keep Courtois, a lot of areas need investment.
Napoli have good history obviously have the big 3 players, and regularly turned a monthly profit in the save I did with them so finance wasnt an issue. Bit of a job holding on to Cavani though, but if you can you can build your sqaud around Cavani, Lavezzi and Hamsik. They have a few decent CBs as well. Should be champions league material and with the right players could over take the Milan clubs and Juventus. I'd say this was my favourite save out of the 4, they have the most ground to gain in terms of trophies, repuatation and stuff.
Arsenal was a fairly easy game aswell. Van Persie is world class, Song, Vermalen, Sagna, Wilshere are all more than capable of winning a title. The sqaud is huge, so many youngsters are out on loan that wont ever really get into the 1st team so you can sell them all off to raise money, not that arsenal need the money. They have the biggest transfer budget of the 4 clubs, the best finances, best facilities, and biggest stadium (I think). They are also prone to a take over maybe 5 seasons in. Again arsenal are well known for thier excellent youth players and produce good regens. The challenge here is to take them all the way and no longer be the 'nearly men' of the EPL...which frankly isnt very hard with thier budget.