Hi there,
I send the updates at the same time to every place. The difference is among vendors:
Google Play: They get the file and send it out to everyone. It's automatic and it can be fully public from in 5 minutes to a few hours.
Amazon: They review it. Usually takes 3 to 5 days before they accept it and make it public.
Apple: They review it. Usually takes 7 to 15 days before making it public.
Samsung Apps: (I'm not sending it out that much to this right now). They usually take 4 to 7 days.
Windows Store: (I will begin sending it to them soon). Usually 3 to 5 days.
Those are estimates based on my experience, but it can vary randomly. For instance, sometimes I've got Apple to approve it and make it public in 24 hours and there was another time that I've waited for months! The reviews are human based, so depends on whether the reviewer is a fast and smart guy or slow and... you get it.
I hope that explains why Android gets all the updates faster.