The T240S model with an ortho belt added. Helps cushioning, hurts reliability in the long haul.
Unless you just must have the ortho belt, stick with the T240 model. Most people don't realize that an ortho belt can weigh up to 5 times the weight of a regular belt. This creates strain on the bearings, holds in more heat that causes the belt to wear quicker, causes the drive system to be less efficient and work harder, and doesn't absorb nearly as much shock as a good cushioning system or even a good pair of shoes.