They are two completely different cars belonging to different tax and drive classes and there is no comparison.
Swift comes in brand new having 1328cc, with no notable features u won't find in a passo. It has a certain market value due to local assembly. It's a different car when it comes to fuel consumption naturally. I own one and it gives 11-12.5kmpl in local on hi-octane having done 2000 on odo with full ac. Due to the bigger engine it doesn't give any lag or slack if given some load. Spares aren't cheap here either but they are abundantly available on dealerships.
Passo is JDM, 1000cc different category of economic feature loaded hatch backs with expensive spares which may also be absent in local market. It has a high market value, but it's resale in the coming years will be under pressure from other newer jdms. Passo does anything from 14-17kmpl in local with ac. However if you load up the car it does put the engine in stress.
Overall I think the decision matrix having these two cars is basically flawed. There is no comparison between them. But it all comes down to what u prioritise in a car and what you hold most important.