Ouch. I can see this thread heading for a nice debate to come...
Well, in defense of Clive I need to speak with the punkrock half of my brain - the part that says "fuck techniciality and competence behind an instrument. It's all about the FEEL and the VIBE that you can project out of it." Clive was a caveman on drums for Madien. Heavy-handed, aggressive, and fully aware of his own creativity and what would help define undoubtedly one of the greatest metal albums of all time ("Number of the Beast").
Nicko, however (in comes the more metal half of my brain that says, "It's all about knowledge and skill, and using those traits to blow the average musician away"), is a brilliant drummer and mandatory for the more technical styling and intricate direction Maiden took with that incredible masterpiece we know as "Powerslave." Nicko isn't half as hard of a hitter as Clive, but he could easily blow Clive away in a competition.
The only real sincere thing I can say about the differences between these two is this...
"Piece of Mind" is my favorite Maiden record (and I stress a big difference between BEST and FAVORITE - such as two drummers, in particular). And even though I already love it for what it is, I feel it's missing something. Maiden still hadn't totally taken their already admirable technicality to the intense direction that "Powerslave" was to bring. Thinking in that sense, I bet "Piece of Mind" would've been a much better album if Clive had drummed on it. So yes, I still have to agree with Dickinson's statement.
Although this is a highly unoriginal (oh, and slightly, well... OLD) subject, I suppose I could use the entertainment!
What can I say? Most of my drumming influence came from guys like Dave Grohl and Chuck Biscuits. I would think someone listening to Nirvana's "Nevermind" album (Mariner - as stated above) would appreciate drummers like that more