I've flown KingFisher and SpiceJet on the route. KingFisher has a full service 320 with First and would be my first choice. The SpiceJet fares are usually cheaper and they have 2 flights so you might want to check them out as well. Never flown Indigo on this route.
If there's fog in DEL in January, expect your incoming flights that leave DEL in the morning to be delayed.