I have traveled to JFK from Mumbai (BOM) and return two times and my experience with Delta is better than others (Air India, Aeroflot) if one is considering economical flight with average comfort level and relative on-time schedule. Although, I’d faced great delay with last DL 16 flight from JFK to BOM when they canceled flight and we were wandering on JFK and hotel for more than 24 hr, later I found the reason behind delay was inevitable considering unpredictable weather and snow at JFK which caused more than 50 flights to stuck ahead of us. Otherwise, Delta has maintained their on-time schedule in fairly right time frame.
Surprisingly, all passengers of that delayed flight got 250 $ delta dolors in a month which helped me to purchase domestic delta connection ticket! On-board meal and entertainment are relatively better than economy flight and DL 17/16 flight has better seats, meal and channels to kill nearly 14-15 hr of non-stop flight. I have hardly heard of baggage problems with Delta.
In my view, it would be a good experience to fly with Delta rather selecting connecting flights from India to US in economical segment.