What model 563 did you have?
I have used many 563's, from the firs with no letter, to the "C" model, "D" model, and my most recent "E" model. They all climbed very good. 2.5:1 slopes are no problem with any, and they all push dirt like they are closely related to a dozer. I have even used them to spread piles fron 35 ton artics in the fill when there was no doxer available.
Tha Cat rollers climb better because of a dual pump drive. one pump for the drum, the other for the tires, so it acts like a no-spin. Others like IR, Dynapac, and the rest have one pump, and when either end looses traction, all the flow goes there, and none is left to turn the end with traction. Just like an open differential in a truck.
The only other ones I have heard about that will climb is the Sakai with tracks on the rear instead of tires, but I would stick with a Cat myself.
Maybe something is wrong with the newer machine?