if u hv been decide i20 to puchase then its easy to find out the model between diesal or petrol.
actully its depand only on how much k.m. u have to drive in a month.
if u hv to drive basically in city only then petrol version will suite u coz of low mentinence cost, bt if u have to drive for long distance regularly then diesal model will suite u coz of low running cost.
its the only theory in india fo choosing a cas. i20 is a very good hatchback.
i hv i10, so i hv no long experience about i20. although i hv been drive i20. its on road driving and prformnc is really awesome in its class. korean compny is really doing good here in india.
best of luck......