Great article. I think the variety of apps available for more creative post-processing is much better on the iPhone than on the Mac. Also, usually either free or cheap on the phone, and very pricey on a Mac.
Is it possible to move an image taken with a different camera onto the iPhone for post-processing? I know how to get images into Photos for iPhone, but it seems you would need to get them into the phone's camera in order to process using these apps.