We don't like ortho belts on any other machine than a True. They have been doing them so long and have figured out how to keep the belt from being a detriment to the drive system. With all of that in mind, if you like the PS100 with the regular belt, you will love the PS300 with the ortho belt.
If you are having to stretch to buy a True, the PS100 is the first model I would buy personally. For the extra $200, the ortho on the PS300 is well worth it with True's patented deck system.