1- Kevin Moore made DT more progressive with his style. Jordan Rudess made DT metal-ish. I don't like his toys.
Ironic since he is probably the least metal of any of the current DT members. I think it is more accurate to say that his presence has made them focus on chops even more, since they now have a keyboard player who can go note for note, shred for shred, with John Petrucci at the drop of a hat, and be happy doing it.
Besides, DT's alleged more metal stuff most likely stems from Portnoy's love for many modern metal bands.
ELP - Even though Keith Emerson was the mastermind, primary creative force and visionary behind the band's music, his keyboard playing wasn't all that great. From a purely technical standpoint, he might have been the weakest musician of the 3. Emerson's ideas translated wonderfully to the big sound of the Hammond Organ, but some of his limitations became apparent when he moved to the piano.
I thought that was kind of common-knowledge.
Not to my knowledge, it isn't. Keith Emerson, in his prime, was a beast on the piano.