okay...
Taking the Mini and iPhone out of the equation, what do the tablets do that the others do not?
Why?
I own a Mac Mini, a three month old Surface Pro 3, an iPhone 5S, iPad Mini Retina, Nexus 7, Nexus 4, Note 4, Note Edge.
The Mac Mini is mostly just an iTunes server my ATV and I use the Surface Pro 3 just as much as I use my Note 4 and Note Edge.
There are things I can only do on the Surface Pro 3 that I can't do on any of the other devices.
Taking the Mini and iPhone out of the equation, what do the tablets do that the others do not?