I think the non-iPhone argument is that you've got less competition. There may be five hundred iFart apps on the iPhone, so your ability to crack that market (hehe, crack) is nil, but you could have a shot at being the #1 fart sound generator on Android.

Also, by going with a non-iPhone platform, you may have a better shot of attracting helpful attention from one of the phone network vendors (e.g., Verizon) who might say "wow, your fart generator is fantastic; we'd like to include it on every phone and pay you a stack of cash." That's just not happening with Apple.

Fart jokes aside, another benefit of non-iPhone platforms is that you can gleefully violate all the rules that Apple enforces on what you can and can't do. If you want to do a better mail client or a better web browser, knock yourself out.