I would say that depends on what you are looking for. There are many of those and many different ways of going about that type of effect. My favorite, which is not necessarily a 'chorus' by definition, would be the Soundtoys Micro Shift.
What is your budget? You asked for the best...
I agree that there is no "best" anything. That being said, and budget aside, if I need a pitch shift/chorus, I'm going with Eventide H3000.