If I end up doing Android I'll probably just use the Visual Studio 2015 android tools. I know iOS apps are more likely to generate revenue through the app store, but is the same true of ad revenue? (I don't know, actually asking). I mean are iOS users more likely to click ads in their app than Android users?
How hard is porting apps between iOS and Android? Obviously Objective C is out of the question if I want to port something, but is it hard to write iOS apps in C++?
Soooo I've been busy with too many things at once but to tackle this head on.
Most iOS and Android games are written in C++. You can do C++ in Android with the NDK, but one downside is that the binaries you generate are no longer architecture independent. Fortunately there aren't too many Android phones running around with Intel or MIPS processors.
In both cases, the UI frameworks are in Objective-C and Java, respectively, and most C++ to Obj-C or Java requires some FFI work. It's nicer in Obj-C because there you can just compile a subset of your code as Objective-C++ (ha. ha. ha.) or create C interfaces that call C++ code in the implementation of your functions, and have Objective-C call those C interfaces and never touch the C++ world.
Java, well, last time I checked you kind of have to deal with JNI bidness if you're planning on working with C++. Not the worst, but it's JNI, so it's a wrapper solution much like what I described with the C interface shuffle dance.
Swift is... early, so uh don't use that if you're planning to leverage a lot of C++. The only way to have Swift play nice with C++ right now is to wrap C++ code and calls with C interfaces or do much the same with Objective-C++ objects acting as interfaces. And Swift has its own peculiarities with working against advanced Objective-C and C preprocessor bits so don't dive too deeply into that just yet if you're coming from C++.
All told, it's easier to work with the native frameworks in the languages they're written against than to deal with FFI-ish stuff.
I see the Big Nerd Ranch Android book was recommended to start with. I think the friendliest book to learn iOS and its frameworks and Xcode happens to be Jeff LaMarche's Beginning iOS Development. Unfortunately the iOS 8 version has gone Swift only, but
the iOS 7 version still remains Obj-C friendly. For the latest and greatest iOS I'd also recommend
BNR's iOS book and not just because Aaron used to be NeXT's documentation dude and the author of the sole book on Cocoa on Mac OS X for a number of years. It's a pretty solid book.