Marathon , as I understand it, has used Valid for a long time. Before Prevost got into slides. Depending on which converter you are speaking , Marathon and Featherlite were the first to introduce slides on the Prevosts.
Liberty was late to the game and waited for Prevost to come out with slides.
Valid has been around for a long time, it would not be a deal breaker for me.
Prevost is now on their 3rd generation of slides and with them they have re designed their Prevost coach to change the
structure of their coach. Now , the slides are not part of the integral frame of the coach, Prevost redesigned their frame
so the truss like frame is below the floor level. It used to be above the floor level and the slide was cut into the truss frame.