Microsoft is better for developers than Apple. I know this sounds like heresy in this new Apple-centric world, but it's true. Furthermore, it isn't even close. Here are 4 reasons why:
1) There are more Microsoft devices and they are worth more
It may be that if you add up all the iPhones, iPads, and Macs in the world, you get a larger number than the number of Windows PCs (or Windows devices not including mobile devices that don't run regular Windows). But the sheer numbers don't matter, it is how many devices there are factored by how much money a developer could reasonably make by selling a copy of their software to the user of that device. When that is considered, Windows wins. By a lot. A developer can make a lot more money by selling software to a Windows device compared to a iPhone, or an iPad, and even a Mac, although the Mac price might be close. But there are still a lot more Windows PCs than Macs. And a developer makes far less selling to iPhones and iPads. Even if there are more of them, it doesn't matter. Prices are so much lower on those devices that it doesn't matter how many of them there are. Windows is where the money is as far as software is concerned and this was true 20 years ago, true 10 years ago, and still quite true today.
(As an aside, Android is even worse than iOS on this comparison. Per device, you can't hardly make anything selling software on Android devices, far less than even the small amount iOS makes).
2) You don't pay a 30% Apple tax to sell to Windows PCs
To sell on the Apple AppStore, Apple takes 30% of the price of every app that sells. While Microsoft has a AppStore on Windows, it is not the primary way software is sold on Windows. You can sell on Windows without paying the 30% you have to pay to Apple.
You can sell on a Mac without paying the Apple tax as well, but again there are far fewer Macs than PCs. The Mac at least avoids this tax, so a developer can make a business selling Mac software without the Apple tax. But not paying that 30% makes a huge difference in revenue between the platforms.
3) You don't have to get your Windows apps approved
When you sell on the Apple AppStores on iOS and Mac, you have to submit your apps to Apple and get them approved. Apple can, and will, reject an app for any reason. They will even reject apps for no reason at all. Even if you do get an app approved, it takes about a week in the best times, and can take a month or more if you have to deal with rejections along the way.
On Windows, you just upload a new version to your web site and you are done. No reviewers, no rejections, no delays. Much easier.
4) Microsoft cares about backwards compatibility
Microsoft cares a lot about backwards compatibility. When they release a new version of Windows, they make sure that applications that ran on previous versions of Windows still work. Of course, there may be an application here or there that gets broken by a new version of Windows, but by and large everything works, and for a long time. You can still run Windows 3.1 applications from 20 years ago on 32 bit Windows 10. You can even still run many old DOS applications from the 1980s. In Windows, old stuff just works.
On the Mac, you are lucky if an application from 5 years ago still works on the latest OS X. On iOS, you are lucky if an application from last year still works on the latest iOS. Apple not only doesn't care about backwards compatibility, they seem to go out of their way to deliberately break older applications. It's like it is company policy to do it.
This is why Apple has never really caught on with business users and why it never will (unless they change their ways). Businesses require that the applications work for a long period of time. For example, I recently was in a computer store and the store's point of sale application was running in a DOS box on Windows XP. In 2015. And the biggest irony? It was a store primarily for Apple products.
Because of these reasons, developing for Windows is simply a better choice for developers than developing for Apple OS X or iOS. And with the rise of Windows 10, it looks like this is going to continue for awhile.