I tried the IRS. It is by far the most flexible of all of them. The Warpspeed has terrible torque steer. The BMI is the one I finally settled on. It is by far the nicest design, fit and finish. For the price, it really can't be beat. It is very stiff and therefore responds very well to minor adjustments. If you want to use stick packs. I would recommend puttind a strip on either side of the battery slots or an impact may have some terrible effects.