There are some great call-outs here. The Mini should really be the default size for the iPhone as having the smaller screen (and battery....) makes it a loss less useful for social media and gaming, ie all the negative distractions. Its a great little swiss army knife of a gadget.

The iPad Mini then kind of becomes the social/gaming device but because its so much bigger than an iPhone its better as its not in your pocket and a constant distraction. Its also brilliant for drawing, note taking and reading.

And you have your Macbook for just doing work on.