The Maruti Swift and Ritz are powered by same 1197cc petrol and 1248cc diesel engine. Both the cars deliver same power and performance but Ritz is more fuel efficient than swift. While Swift is popular, reliable and have good resale value than Ritz. Now you are the best judge.
You can compare Maruti Ritz and Swift through given link in highlighted body text.
Maruti has a good and vast service network and there will be no problem of maintenance and replacement of parts at later stage but the resale value of the car might decrease as the company has decided to discontinue the vehicle. Despite this, there will never be any shortage of parts as manufacturers make parts for next 10 years. Also, as Ritz share a good number of parts with its sibling Swift there will be no shortage whatsoever. If you would like to consider, the Indian auto market has many other offerings in the same segment such as Tata Bolt, Nissan Micra, Ford Figo, Honda Brio and Grand i10, Maruti Swift, Chevrolet Sail hatchback.