the discussion going on isn't really helping the guy!
to be honest, people saying swift is overpriced are wrong, to some extent. Not that swift isn't, but city is too! what do you get for 16.70 lakhs? an automatic 1.3 l car, with no nav, no airbags, lame tires, no alloys, no rear speakers, not even keyless entry, shitty shocks! this is Pakistan! everything you buy isn't worth its true value!
so the argument for which car is successful and which isn't is of no use, both the cars belong to a different category and were manufactured with a different consumer in mind!
the things that'll help the guy are, which has better :
consumption : city has very poor consumption! specially auto.. locally. on long drives its fine. but it does depend on your driving style too! (don't know about swift's consumption)
Parts : that we all know, suzuki parts are cheaper.
Comfort : city is not very comfortable, but since your a teenager i don't think that should stop you from buying it.
Price : swift is cheaper but city has more stuff to offer, i.e boot in the back, the car being a honda rather than a suzuki :P, easy maintenance. more reliable.
Fun to drive : i've driven the city and it is a nice car to drive as a teenager, it will give you that extra power you want but not so much, just so you won't kill yourself.
modifying/detailing : swift looks better modified, as its a hatchback, adding body kits, rims and a spoiler will make it look better.
Safety : both the cars are equally safe. equally stable. at least the city is, don't have first hand experience with the swift so don't know much about it.
Speed : both are fast enough for you !
hope this helps.
in the end i'd like to say, you should drive both cars to get a better idea and buy the one you like!