We were at our best last year when there was flexibility in the front line. Tevez offered that as he drifted and came deep. Aguero would also offer that, someone like Drogba and Eto'o wouldn't. I think Mancini is thinking along these lines, as players he has admitted to liking such as like Sanchez, Lavezzi and Cavani offer that flexibility too. Dzeko offers a different look, and that is his role. I rate him.
Those saying we don't need a 1st choice replacement are missing the fact that we are playing 60+ games next year (hopefully) so there will be plenty of rotation between the attacking options. Mancini wanted another striker anyway, so I can see us bringing in two.
Like the majority Aguero just seems to make sense, and as for him not settling, yes that's a possibility, but look how well Suarez has settled for Liverpool and how badly Torres settled at Chelsea. Whoever we sign is going to be on some level a risk.
Alternatively I wouldn't mind Higuain, but my 2nd choice would probably be Hulk