The 52 cal requirement was not for the light howizter. It was always going to be 45 cal or 39 cal. ST Kinetics was going to upgrade their guns to 45 cal if selected.
The two original contenders were M777 and ST Kinetics Pegasus. The M777 is lighter and a proven system. The US Marines have ordered several hundreds of these. The Pegasus, while heavier then the M777, has its own powerpack, like the bofors, that allows it to shoot and scoot. The gun can move short distances using its own power pack. The IA loves this capability (if fact this was one the main features cited that tipped the balance in favour of Bofors as opposed to the french gun back in the '80s).
Also, at the time of the original tender, BAE didnot show much interest in offering the M777, as the production run for US marines and army units is going to continue for well over 1,000 units and delivery for Indian purchase, if finalized would take years. Hence the IA preferred the pegasus.
Now with the FMS route , I think the delivery time problem would have been taken care of, somewhat.
All in all the the M777 is very capable system, its the lightest in its class and is a proven system.