Hi,
If you have a VISA to USA to travel for interview in future then i suggest u choose buffalo office itself hoever if u dont have a US visa to be able to travel to US in next 1-2 year then applying at buffalo will be risky as obtaining short term visa for US in India also is a big challenge , sometime they reject it outright so in this case u request for a change of VISA office.
SO i suggest u do this -
2) you apply with all the forms and proofs to buffalo office with a note highlighting change of address
3) Normal Process follows
4) pls remmeber after your PR is approved you will have to travel to US to present your passport as you cant courier indian passports from India hence this is a limitation.
Also if you want to take chances with Canadain EMbassy in INdia then go ahead, as per new process processing will be faster in india as well however i have some doubts over it due to stiff comptetion in India.
Also the VIsa office change itself may take some time, and it might be tedious process.
I hope i was clear.
Thanks,
Rahul