I've tried both quite extensively. FWIW, iPad Pro _feels_ faster and more fluid. Still not the right device for me, but I had no complaints wrt performance. I did not buy iPad Pro though: not the right device for what I do. I did buy the Surface Book, but took it back to the store a couple of days later. It was bluescreening a couple of times a day seemingly due to driver issues. Its UI performance was choppy as well, particularly scrolling non-WinRT apps such as e.g. Chrome or Firefox. This was basically the top of the line Core i7 model, so I expect that things are even worse with the lower end models.