BOM issues are primarily during the Monsoons, in the summer. Things get flooded, weather is crummy, ontime performance sucks, etc.

EWR issues affect afternoon flights year round(and I'm sure you know about the terrible crosswinds).

I'd fly EWR-BOM on AI to be honest. I wouldn't be able to justify spending more to not fly through BOM in the winter - your chances of delays should be low.

AI operates EWR-BOM with their newish 777s, so MX problems are rare...

Note with BOM - make sure you book with AI all the way through to BLR on the middle of the night Air India flight - transfering to another airline at BOM means you have to trek it out to the domestic terminal, which is a bit of a headache.