Which one is the best app platform ios or android?

What kind of app?

I would choose android, because of more user base in India. If the app is more advanced , is expected to garner revenue and is expected to be popular in other countries as well , then iOS.

Who are you making the app for?

 Thanks for the reply but I want to know about which platform is best if you make an app like google allo app so which platform is best for this app.

I guess the world need more developers for Windows OS... well, because Android and iOS already have a lot. Sometimes it does pay to develop apps for an environment that isn't saturated yet.

Sir world need more developers ..... but today demand only android and ios, because every one make an app on two platform ios or android. so tell me which is best?

Depends on what kind of app you are looking for. It's been asked two times already but you're ignoring it. If you cannot provide the relevant information and the purpose of this thread despite people asking for one, I'll have to close this thread.