Full disclosure: I'm biased as I'm primarily an Android engineer. But, I've led teams and developed extensively for both platforms, so I'll tell you a couple things I've observed.<p>1. If you already own an iOS or Android as your primary device, that should play big into your decision. You'll have a much easier time maintaining interest in your project as well as being more likely to create a more compelling product if you live on the platform.<p>2. Google's Android documentation and guides are on a <i>completely</i> different level than Apple's for iOS - Google's is just so much more extensive. It's really not even close IMHO. If you're a beginner I think this will make a very large difference.<p>3. The iOS developer program and provisioning system is a PITA, even for experienced developers. Often times when learning something new, all it takes is a small roadblock to become frustrated and lose interest. With Android, building apps for you and your friend's devices is very easy, and submitting to Google Play is <i>much</i> easier, with no review process and again just one guy's opinion, but despite a recent (and dearly needed) makeover, iTunes Connect is still inferior w.r.t usability compared to the Android Developer console.<p>4. I used Eclipse + the ADT plugin for years and while it wasn't terrible (I was come from J2ME development for BlackBerry so the bar was quite low), I was always jealous of Xcode. Google has now addressed this with Android Studio. It's still a bit of a moving target, but I now consider on par or better than Xcode.<p>5. Don't let the haters scare you away with the fragmentation arguments. "Fragmentation" is a feature :) Truthfully, if this is just a side project, I would set a minSdk for your app a minimum 14, or even 19 if you want to, and be amazed by how your app works so well on the 100s or 1000s of devices out there that it supports.<p>Couple words on iOS:<p>1. Whereas with the x86 emulator and Genymotion, the Android <i>emulator</i> has dramatically improved, the iOS <i>simulator</i> is still superior with respect to ease of use and pace of development.<p>2. If you go the iOS route, I would strongly suggest to go directly to Swift. It's where the puck is going and you've got a chance at this point to be a relative expert among a sea of objective-c developers, who will need to learn it as Apple increasingly shifts the platform.<p>3. This is very subjective and nebulous, but after using both platforms extensively, I've found the iOS APIs are simply better. You'll find things <i>just work</i> and you'll be continually surprised to find the puzzle pieces just fitting together. (ie "hey I wonder if there's a way I do X...oh perfect there's just a simple method call for it")<p>4. As others have noted, if you don't have a Mac then the point is moot, Android is your only option.<p>Hope this helps!