The main difference between the T-bar and the side support bars is the location of the bar on your bellicon. If you prefer to hold onto something in front of you, the T-bar would work best, while the side support bars offer support on both sides of you when you jump.
The T-bar offers stability in the front of you as well as the added ability to get quicker, more endurance-building cardio workouts such as SwissJump workouts.
*Right now, the T-bar is only offered with the bellicon Plus model. There is not a separate T-bar attachment for the original Classic and Premium models.
The Support bars offer more support, as they are resting at your side rather than in front of you. These are typically purchased for seniors, or individuals who have trouble with vertigo or balance.