For an accurate comparison of render speeds you must keep the conditions as similar as possible. Running 5.01 and 5.5 simultaneously, or with other apps running, may tell you something but it won't tell you anything valuable about their relative speeds. Creations's comparison of Bryce5 running alone vs Bryce5.5 running alone seems to result in times that are in the ball park of what DAZ is saying should be expected. Five minutes, seventeen seconds is a substantial speed improvement over eight minutes, forty four seconds. You'd have to have a fairly big jump in processor power to get that improvement in Bryce5.