It's 2017 and I have a great mobile app idea. Start with Android or iOS?

Why not hybrid mobile?

How much do you want to spend to get started? It only costs a simple one time $25 developer fee for android, for ios its $100/year. If you are just getting your feet wet going android is much cheaper, then if you make money on android you have a budget to get a mac with xcode, an ios device and the $100/year fee to write for ios.

The report summarized here (for Q2-2016):

http://bgr.com/2016/07/20/ios-vs-android-developers-profits-...

shows the Android store with twice as many downloads but half as much revenue. The importance of this is going to vary depending on specifics about your application - does it need a strong network effect to deliver value, or is it valuable for a solo user?

react native

Doesn't matter if your idea sucks.

I'm going to be that guy. Sorry.

Are you sure it's a new idea? Have you really searched the 2million+ apps out there to be sure? Truly new and original ideas are rare, most things you can do on a mobile have been tried at some point in the last 10 years. Check again, and learn from what others have done.

Have you validated the idea? I don't mean asked your mates if they like it. I mean have you got someone to give you money as a pre-order?

Do you know exactly who your market is and how you'll reach them? Putting something on the app store is not enough, it'll vanish without trace. You need a marketing channel outside the app store that can get to your target market and tell them about the app.

Have you tested that marketing channel? Personally I would do this before writing any code. If the marketing channel doesn't work then you need to find that out first and find one that does work. Don't worry about advertising vapourware, if people really want your app they'll wait a bit (see Kickstarter for evidence).

Unless, of course, this is a side project that is never intended to make serious money. If so, then pick whatever technology and platform you want to learn (I'd second React Native as a tech to learn). Market sizes don't matter if you've got no customers and no channel.

It honestly depends on how complicated your app will be, and how talented you already are as a developer.

But in truth, you should probably be looking at making your Minimal Viable Product in whatever you are the most comfortable in. Because you'll want to get it out and in potential customers hands as fast as possible and prove that your idea really is as useful to people as you believe.

I'm also going to take a stab here and say that you're probably not a super experienced developer, because trying to launch and support an app across two different platforms in different languages almost simultaneously isn't an easy feat to manage.

For the sake of discussion could you elaborate on why native code will be more efficient/productive?

Is it the additional layer of abstraction? Or is it an issue of the uncanny valley?

I understand that you may not want to discuss anything proprietary to your app, but I'm interested in understanding your thought process.

How about starting with a web site? It is much easy to iterate and validate the idea. Once you get enough usage and feedback, then start to build app.

Use React Native which will help you to make for both platforms faster, here is a good tutorial to start with: https://reactjs.co/react-native-convention/

I build for the web so I'm obviously biased, but have you considered building a web application?

If your app doesn't use device features that are not exposed to the browser, building a progressive web app (https://developers.google.com/web/progressive-web-apps/) will save you a lot of effort, help you get to market faster, and spend far less money on user acquisition than a native app. On iOS, PWAs look and feel no different from regular websites. On Android, you get access to native-like features, including support for loading the app offline, push notifications, the ability to install the app to the homescreen, a separate entry in the task switcher, etc.

I wouldn't build something like Snapchat or Instagram as a webapp, simply because building those experiences in the browser and getting them just right is still kinda hard. However, most applications aren't Snapchat or Instagram, and a prototype certainly doesn't need that level of spit and polish.

You might still choose to build a native app somewhere down the line, but starting with a webapp gives you a chance to evaluate your idea and get something working in the hands of your users very quickly.

I'm in the same boat. Planning to go iOS first, since I'm an iOS developer and don't know Android. Go with what you are most comfortable developing.

React Native might also be a good choice. I was pretty impressed with what it could do on iOS, but I had challenges getting it to work on Android.

As a sole developer who recently released my first mobile app, I can't comment on your specific use case or generalize about the market as a whole, since I don't have significant experience. That said, I chose to use React Native and release to both iOS and Android. After three months without doing any serious spending on marketing, my iOS version had an order of magnitude higher installs than my Android version. I suspect this may derive from differences between Apple and Google's search ranking algorithms. It's a moot point for me, since React Native supports both platforms, but the single data point may help you.

So, I don't have direct experience, but folks talk to me, so I have anectdata. ;-)

If your revenue model is app sales, go IOS.

If your revenue model is mobile advertising, you probably want to go Android.

Beyond that, it gets complicated, but I think the following are valid (though your specific user segment might flip the other way on each of these):

Freemium models (ie. a free app that you can upgrade to a paid version) should probably go Android first.

Free with in-app purchases (eg. F2P games) should also probably go Android first, but it is not as clear-cut.

If your revenue model is transactional (eg. flash sales), go iOS first.

No matter what, list your assumptions (that users have the problem your app will solve, that you know the language they use to think about and describe their problem, that they are actively looking for a solution, that they will be willing to pay to solve their problem, that they will be interested in your solution, that they will be willing to pay for your solution, any assumptions about their price sensitivity, your assumptions about reaching potential customers to make them aware of your solution, your effectiveness at turning "lookers" into "buyers"), and aggressively validate and de-risk all those assumptions.

Good luck!