Clive's style was looser, edgier, more toms, more raw energy. It rumbled and rang open. Definitely a punk influence to it.
Nicko's style is straight up prog rock, very technical, tight, clean, complex, plenty of change-ups in beat division, tempo, and time signature. He's right there with Neil Pert or Terry Bozzio. Sometimes a drummer like this can get too complex, and lose sight of their basic job of keeping time and establishing a backbeat. Nicko falls victim to this at times. Also his snare choice works against the song sometimes.
So I voted for Clive, partly out of respect, and partly for the fact that I would choose his style for my own music.
But I agree with the sentiment that each drummer is right for their era and the material they are playing. After Nicko joined, Maiden got progressively more progressive, and Clive probably would not have fit in as well. Just as Nicko's playing may be a bit too self-conscious and cerebral for the raw attitude of the early albums.