Del-Jai-jdh-udr-Bom doesn't exist. They all are separate one stop to Bombay now.
OP make an itinery and let us know. Certain airlines on certain routes will be better than others. Depends on where you want to go and how. Ai has the Max legroom in Y. There are pluses and minuses for all airlines. And all will get you to your destination. If you are not very particular majority of India goes for the cheapest fare irrespective of airline.
Cheapest way to get ticket could also be the particular airline website. Or sometimes it's not. For some buying return fares makes more financial sense sometimes it's better to go for one way tickets. Start your basic search from cleartrip and take it from there.