i own a Swift 2012.. and one of my best friend has a Passo
well Swift is 12 Km/l in city with AC on.. and Same goes for Passo with AC in city
BUT, it varies ALOT depending on your driving style
To b honest, both are very good cars.. If you like Manual, go for SWIFT, it has better pick etc
If you like the comfort of auto, Go for passo.. Plus it is safer (airbags etc).. But Ground clearance is an issue.. On most Pakistani speed breakers, it will hit.. unless you get bigger tyres etc..
So it boils down to Manual vs Auto.. Also everyone will give his opinion which maybe biased..
look at both cars.. then whichever car your heart says, buy and enjoy