Sarzo is a good player himself, but his dramatic stage antics belie the fact that he actually has a laid back groove that has none of the forward drive Daisley's bass style has. Plus Daisley has that pick attack. Daisley is very accentuated in the way he plays, you hear every note.
Just listen here, Daisley pre-Ozzy:
Sarzo playing the same song:
Some people might actually prefer Sarzo's more massive and modern sound, but there is no denying that the notes are more focussed with Daisley.