dear I am using City 2003/04 automatic , on CNG and have faced a full summer season on cng with A/c running fully. travelled to long distances also good average on CNG and Petrol. Annual toke is little lesser than Civic being 1300cc instead of 1600. City does not give any jerk during shifting to next higher gears as it is vario.
Civic being 1600 cc has the power and pick better than city, if you go for civic than choose 2005/06 model. also city 2006 is recommended. any way city 2003 without CNG is a gain, you can install CNG in it by expencing about 60,000/- margine price. go for city 2003-5 with above recommendation.
Regards.