It would be best if you drive a city and try it out for yourself.
Having personally driven the 1.3 AT, here's what you could expect: upon flooring the gas pedal to gain acceleration via a down shift/kick down, sit back relax, heck type out a pending email and by the time you are done doing this - you still wouldn't have lost out on much! There are times when you need the boost, for an overtake for example - just won't happen on the 1.3!
The 1.5 tends to behave a little better than its little brother - but then again don't expect miracles with it either.
Moving from a swift to a AT city would definitely leave you, cursing the decision.
The manual on the other hand is a different story all together on the other hand.