This may be partly because the DualShock 4 (and I'm sure the same goes for the Xbox One controller, even if I have not tested it) is a massively superior control solution compared to the minuscule sticks and limited ergonomy of a portable console. (dualshockers.com)
It's truly a lesson in ergonomy that could be learned by others, too. (drivemag.com)
The difference in performance most likely came from improved running ergonomy. (compressioncarl.com)