The obvious difference is that "Black Piet" is intended to represent a black person,

His defenders would often argue he's black because of the soot encountered going up and down chimneys. Somewhat in contradiction to the broken speech and accents (often like a Surinam creole)he widely speaks/spoke in.

But the point was ofcourse the arguments used , tradition, it's 'ours', it's been always like that, it's PC, who are they coming here telling us our traditions are racist etc etc are very similar.