I've got this "dedicated device" principle that I like to stick to as much as possible. Back in the day when I had the iPhone 4 and then the iPhone 5, it was easy.
The phone was for, well, phone things - calling and texting. Oh, and I used it as an eReader.
The iPad was for games and working on the road.
The iPod Nano was for music, obviously.
Today, the lines have become blurred, thanks to the changes in device sizes.