[Oyk]

I think it depends on where the Indians come from 

It's like asking which is correct... jiak png or sek fan. Both are correct. 

As for me, I grew up and old hearing Deepavali so this one sounds familiar to me. Diwali sounds foreign. Hearing it would be like hearing 吃饭 not in Hokkien or Cantonese which I am comfortable with but some other tiongkok dialect which I am not like the Wu dialects... those I heard in Wuxi, Suzhou and Shanghai.

Btw you don't need to go to China to hear other tiongkok dialects. Every so often I'd hear tiongs calling home and speaking their mother tongue. Sounded very crude, loud, uncouth.