These are similar balls.  I would exepect that if you had them drilled the same layout you would probably get a smoother backend reaction on the Heat as compared to a bigger hook on the Fired Up.  Both are good house condition balls.  If you are trying to bowl a down and in shot (lined up to roll the ball straight down around the second arrow with smooth hook to the pocket) buy the Heat.  If you are swinging it out a bit buy the Fired Up.