I've always been drawn to this:
(4:00 min mark for some tasty slap)
Hubert Eaves IV on an MTD, and I like that he uses the technique like a garnish. To use Anthony Jackson's quote of 'slap is the ketchup of the bass world' (paraphrasing) I like it better when it's a spicy mustard that really sets off the dish when used just right. Too much and I need to wash my mouth out.
To0 many slapped notes in succession, at a fast tempo, and IMO a crucial thickness in the low-end disappears and the mix sounds thin and the groove dies.
Marcus would of course be (again IMO) the master at maintaining that fat sound while slapping, and even in that instance, I think he tours with a keyboard player to hold down the 'base' when he's really getting out there.