Best device to play on?

As the post says, I'm lookin for input on what people feel the best device is to play on. I'm fairly new into the game, however I'm in a position to pick up a couple tablets of various models very cheap, so I'm looking to see what people Mainly prefer. I currently just play on my normal iPhone 6 and I absolutely crave a bigger screen to see more clearly lol.

What are other people's thoughts?