I've got both a Surface Pro and an iPad pro and it would be a Surface with an ARM processor, sort of. The sort of comes from the fact that the windows resources are remote in the iPad case which allows for faster response and more media/storage on the remote machine. The Surface Pro doesn't last quite as long on battery power as the iPad does and it can be constrained in its storage space (I've got an additional 256MB SD card plugged into mine and its still tight).

But the interesting thing for me are the two approaches to window dynamics. The Surface Pro is difficult to operate with a finger, ok with the stylus.

Well, no - I realized I have iPad mini, and so for me, iPad = 8.9" screen, 300 grams, can be taken in any bag anywhere, lasts a whole conference even half-charged.

Surface is 2.5x heavier, it's the 'I must remember to, and want to, take a full computer with'.