I would like to have a single 2GHz G4. Just having a dual 1GHz or a Quad 500MHz doesn't really mean you are getting 2x or 4x (respectively) the processing power. I think you actually get less.
There was a discussion a while back that discussed how quad processors only give you a double performance increase.
This isn't really a matter of "preference", is it? It's just a matter of sifting through the marketing BS and comparing benchmarks.
Most of us here know that a single 2 ghz G4 (if such a thing were to exist) would be faster than a dual 1 ghz. Apple tries to spin it otherwise but we know better.