i'd also have a hard time deciding myself.

the weakness of the Mazda3 1.6L is its engine / weight. this may be cured by the 2.0L variant but that might not be within your budget. for city driving - this might not be that be a big factor though.

on the other hand, this is the perceived strongpoint of the Honda Civic. however, the Civic just looks dated and boring.

but still, my vote goes to the Mazda3.