Maruti Swift has a good reputation in the market for being reliable. Although Hyundai Grand i10 also has had no complaints in long-term use. Both the cars have slightly different features and handling. It is up to the customer to decide whether he likes features line the rear AC vents which are in Grand i10 or he prefers handling and drivability which is Swift renowned for.
Can you please give us more details about the number of member in your family along with your budget and the driving conditions of your area. As far as choosing between old and new car is concerned, it will depend on your budget and your personal preference. However, if you want a certified used car with 1 year warranty you can take a look at the CarDekho used car section by visiting the followinglink.