My favorite rock keyboardist is Jon Lord, and one of the reasons I loved Deep Purple was the interplay between Blackmore and Lord. In most rock bands, keys are usually held back and used as "filler" but in DP, Lord had the chops (and then some) to stand on equal ground and do battle with his overbearing guitarist.
I get the same feeling when I listen to Rudess and Petrucci. DT has obviously set up the band to attain a very similar interplay between keys and guitar, and as good as their previous keyboard players were, Rudess is the only one with equal parts ego, technique and songwriting chops who could pull off what Jon Lord did for Deep Purple.