The RT6 hydraulic brake from Magura is the less-expensive option to the high-end RT8. The way to run these would be to use a Magura hydraulic aero lever (included) or a small converter box (not included) for Dual Control levers, that will mount nice and tight under your stem. Although we prefer the lever route, either of these option work well. Now that you know how, the real question is why.
The Magura hydraulic brakes offer less frontal mass for much faster aerodynamics. The hydraulic stopping action is far superior to standard cables. They are stronger and modulate better.
The only reason we can see not to purchase them would be the cost. This is the exact reason Magura offers the RT6. It reduces the cost of the brake and makes it a reality for many TT riders.