The Maruti Swfit Dzire and Hyndai Grand i10 are car from different segment, so it's unfair to compare the. The Dzire is a sedan while the Grand i10 is a hatchback. Both are amazing cars in their own segment. To answer your second question, we would recommend that as your usage is pretty low, please go for a petrol variant. Diesel variants are advisable when the monthly usage is more than 2000 kms a month.
That's great if you are planning for a new car. It might interest you to know that Hyundai is planning to launch the facelift version of the Grand i10 sometime this year around August/September. The Grand i10 facelift is also likely to get AMT (Automated Manual Transmission). So if you are planning in 1-2 months, we suggest you to wait for its new facelift version and other new upcoming cars.