The lure of multi-platform builds are a nightmare in disguise. Any web designer will tell you horror stories of trying to juggle IE with Firefox with Chrome with whatever at the same time. You will not suddenly earn more sales because you were able to launch on Android/iOS/etc on day one. More than likely, your attempts to multi-platform will restrict your app in ways that will kill it on all platforms. Your best bet is to start with one platform, finish that, then build for others. Your end product will thank you.
There are no pros/cons to Cocos2d-x unless you like C++ more than Obj-C.
