I played the switch and PS4 versions back to back over the past hour. Both on the same TV. Dualshock 4 controller for the PS4, pro controller for the Switch. I'd play a minute of one version, pause, change the input on the TV, unpause the other version and play it for a minute or so, then back again. After an hour of this, I am convinced the Switch version has at least an extra frame of lag, maybe two. It doesn't feel as "tight" as the PS4 version. It feels more "floaty" and "loose". (Similar to SDOJ on the X360.) And on the Switch Lite I find the game basically unplayable (due to lag + small screen). So, yep, definitely going to sell it and keep the PS4 version.
BTW in terms of slowdown both seemed more or less identical, though I only tested the first three stages.