Having owned both at different times, I'd say they are about as hardy as a yellow tang and fairly easy to keep. It depends on the individual fish, but my purple has been way less aggressive than my yellow was (I ended up selling the yellow because he was an a-hole.) I got my purple when he was fairly small and a little ratty looking. Now, about 1.5 years later he's about 4-4.5 inches and fairly plump. Adding them as one of the latter fishes helps with aggression too. Mine is pretty chill with most everybody. He chased my butterfly a little when I recently added him, but that's about it.