I tried using a mini, and i DID find it to be much easier on my eyes than my iphone.
I was using my wife's min for my test. When I went to go buy one for the phantom rig, I realized that I could buy an Ipad Air (base model, 16G) for not much more. These Air's are so light that it was not much more than the mini from a mounting standpoint.
I found a really solid mount and went with an Ipad air ($320). Im THRILLED with the much larger screen!
So, mini or ipad- I dont think you can go wrong!