It all depends on what you want from "using a map service"? Why do you want "extensive data" - what does that really mean for the app?
This is absolutely key. Do you just want a backdrop for your own data, do you want to run queries on the data itself. Etc. Etc. Whatever you choose should be the best fit for you.
For OSM - if you want more data in the area, then you add more data in that area. Mostly the data is added by people like you and me. Sometimes it's added when there is some good compatible open dataset that can be imported.
If you want to talk to OpenStreetMappers then one of the places to sign up to is the Indian OSM Mailing list.