Last time I flew to DEL was on CO and Mrs. DCATravel was on AA through Chicago. Her flights left ontime and my connection flight was canceled from IAD to EWR. Only CO flight they could find for me was five days later but I was able to move to Lufthansa for the outbound. I did the return on CO and it was a great flight.
Moral of the story, it's a crap shoot no matter which you go with based on the need for a connection. Missed the ORD flight due to weather and missed the EWR flight due to weather as well.