So it's official, the iPhone 6/6s will offer even more screen space... but, personally, I still find the 4S size to be just right to practice handwriting. Bigger screen, means bigger strokes to draw, and that quickly gets tiring.

So even if I upgrade, I may keep the 4S just to Skritter ^_^

What do you say other iPhone users?

I'm not so sure. It seems skritter recognises my strokes regardless of how big/ small I draw them.

I understand the iPhone 6 will have a function where you can shrink the screen space used down to a smaller size, maybe to emulate the size of an iPhone 5 screen. The idea being that you can still reach most everything with your thumb and still use the device one-handed, but I suppose this would also give you a virtual "old iPhone" space in which to Skritter.

Just from processor speed I find the 5S much better than 4S for Skritter.

Is a matter of preference, I use both 5S and iPad for Skritter and is a very different writing style. With the larger screen I find it much more enjoyable to focus on the shape and rhythm of the strokes. On the smaller screen it's more about just writing whatever Skritter will most efficiently recognize.

The 6 should be fine. The 6S might be a bit of a weird in-between.