Im currently using an iPhone 6.

I previously used an iPhone 4s and 4.

Surprisingly, I found that with the smaller 4 series phones the image was softer. I was expecting it to become softer still with an app not optimized for the larger screen but the reverse is true. I find things much sharper with the 6. Not sure why.

There was also a big jump from the 4 to 4s. Graphics were scaled down for the 4 and I found it difficult to identify braking markers when I moved to the 4s. Even the colour and texture of the ground surface was different.

I also find that the steering is slower with the 6. I'm not sure if this is related to hardware or iOS 8.