Truth be told, there’s no right answer here. The question of which platform you build on first depends on the nature of your app, your core user demographic, and the specifics of your business strategy. And there are strong arguments on both sides.
First, let’s look at some numbers. Without question, iOS apps generate more aggregate revenue than Android apps: in 2016, the App Store generated $34 billion in revenue, while the Google Play store generated only $10 billion. This is spread across 29 billion downloads on the App Store vs. 63 billion downloads on Google Play – effectively meaning the App Store generated three times as much revenue from only half the number of downloads. In isolation, a download is worth more for an iOS app than for an Android app.
This may be due to the geographical distribution of the two platforms. iOS apps dominate in more mature, established markets like the US, North America, and Europe – just take a look at the phones in the glitzier regions of Miami and you’ll see this played out. All of this means that iOS app users have more money to spend on apps, which can translate to more revenue for iOS app developers than Android.
That said, iOS apps come with their own limitations. Apple, Inc. has the final say over what goes on the App Store and what doesn’t. They can reject apps at their own discretion, which means that it’s entirely possible to spend time and money creating an app only to have it blocked by Apple. While rare, this isn’t unheard of.
Furthermore, the App Store has a review period lasting between a few days and two weeks when publishing apps or pushing updates. This isn’t a major problem, but it does mean that the iterative development process can only move so fast. Every new version of your app will come that much slower, which may slow down improvement and user acquisition for early stage startups.
Again: it all depends on what’s important for your own specific app.