No one is going to have a certain answer for you because there are too many individual factors to hazard a likely guess. My personal thought would be that pass/fail grades would likely never hurt you on an application (where as taking graded classes and coming out with a B average definitely would hurt you). Additionally, the P/F seems like it would give you a lot more time to study for the CBSE which is really the biggest factor for residency. Now of course the counter to that would be, if you can get in that top 10% it may make up for a less than stellar CBSE at a lot of programs and could be a boon for you. But my gut tells me that P/F is the safer choice.
But the P/F vs Grade aspect is so uncertain I hope it is only a very small part of the criteria you are using to select a school. Things like cost, education (heavy clinical vs heavy academic), rate of specialization from the grads, and even creature comforts like geography and the school's culture should all contribute to the school you choose.