Both are great go slapping. Low action is good if you don’t slap and pop very hard. This would give very clean sound and effortless left hand movements.
If your style is more heavy handed, you’ll like a little higher action so your string won’t buzz too much. All 3 ladies that play for Prince I would assume would not have super low action Nik West and Ida Neison are slapping Goddesses both bend strings like guitars I can’t imagine playing that hard and have super low action. Rhonda Smith on the other hand may be a little lower because she does a lot of tapping.
Hard Slapping pioneer like James Jameson would definitely have higher action.
I have my basses setup both ways for slapping if there’s a lot of popping in the song I definitely favor higher action, it’s much easier to hook my index or middle finger under. Of course your mileage varies.