As STStech says in the smaller and in the bigger device the energy for the surface of the plate must be the same. But when the diameter of the drums is different this mean (in case of the same sized plates) that in the bigger drum diameter device laser head is not working more time than in the smaller drum diameter device. In other words the bigger device is less effective on smaller plates (just because the laser head working only in smaller parts of time per revolution).
It's mean that Kevin@Kodak giving us right answer.
I ask by phone some tech guys (who are working from years in this sector) and they give me different answers. This is the reason to post this question here.
Thank everybody for their posts.