The usual way, for booking flight trips in India has been, separate bookings for onward and return flights. That is primarily because of two reasons:
1. Better management of changes in travel plans of onward and return trips. Say, if the return date of travel changes, then you just need to change the ticket for return journey, and not for the entire journey.
2. Also there were no incentives in terms of discounts in booking round trip tickets.
But in the past few months, several Airlines have started to give significant discounts on the purchase of Round trip tickets. For example on a Go Air ticket from Mumbai to Delhi and back, you can save around Rs. 1500/-, if you book a round trip ticket vs. separate onward and return tickets.
See the example search below:
1) Onward Booking fare: Rs. 5376/-
2) Return booking fare: Rs. 4976/-
3) 2-way booking (discounted) fare: Rs. 8762/-
So for this travel you can save 1592/- if you book 2-way.
But is there a catch?
Not really, just that you need to read the terms & conditions carefully for such bookings. Typically, if you expect the travel dates to change, then it may be better to have separate bookings, as the cancellation/change charges will apply on the entire ticket.
But if you are sort of sure, of the travel plans, then it is worth while, to book it in a single ticket and save money.
Try it out by firing out some two way flight searches. And let us know, if its helpful: