Hi Robin. I sand wood for several years, but only used Levighetor and planetario. Never tryed a belt sander, only a small portable for small corners and other areas. I've seen wood floors done with a belt sander and I was never impressed. They tend to leave marks if the operator does not have expdrience and knowledge. The final result achivable with a klindex planetario are simply amazing. It will leave the floor flat and if you stick with the corect steps that klindex recomend, you will be very pleased. Cons : on the really bad floor, aneven floors, it tends to be hard on your hands, first step (24grit). After that it's easy.
I don't know anything about the new maxi orbit, and 9 out of 10 wood floors that I do are at least 40-45 years old.