With the short gameweek I'm going to keep this brief. Your basic choice is to either captain your City players, or, if you are worried about rotation (which is a concern) then stick with a proven asset with a somewhat tricky fixture (ie Van Persie and Rooney).
City's fixture is just too good to avoid and if you hold Aguero or Silva it's tough to look elsewhere. As with prior year weeks I think Silva is the safer option, though Aguero probably has the higher upside. Aguero looked sharp early against Arsenal but drifted out of the game a bit as it went on (though I don't really understand why he was stripped of his assist). At this point I am leaning towards Silva, who appears less likely to be dropped (Dzeko must be due a start soon) but it really is a coin toss and I don't have anything concrete to help you make a decision either way.
Outside of the City stars you're left with Van Persie who had a rare off week at City but faces a Villa side who have conceded 7 goals in their last 4 home games. Arsenal are clearly a riskier play than City but that is somewhat offset by the fact that Van Persie is involved in an higher proportion of Arsenal's goals than either of the City pair (the Dutchman has scored or assisted 18 of the 25 Gunner goals).
You could also take a look at Rooney given the last couple of games, though back-to-back home clean sheets for Fulham suggests United won't have it all their own way. If you own him you will of course consider captaining Rooney, though I don't think United are quite at a place where you captain Rooney no matter who the opposition.
I omitted Ba from the rankings last week (by mistake) but even then he wouldn't have cracked the top 3. Players from the non-elite sides struggle to consistently deliver big scores and thus make risky captain picks. Even a fit Darren Bent and his 10 2-point games would therefore not have made this list, no matter how good the fixture is.
I might not get to a full reader questions post this week but if you send them to @plfantasy I will try and reply tonight.