I have Siberian sway bar bushing for front and rear. I used the rear along with the Stillen sway bar. Since I installed them together, I can't comment any difference the bushing specifically makes. Only that the install is straight forward, and bushing itself is stiffer then the OEM rubber. You have to slice the bushing open yourself.
For the front, I actually prefer the OEM because it comprised of the rubber top + hard plastic bottom. The Siberian bushing is made entirely in polyurethane. So, as a whole unit, I thought the OEM would be less squishy along the vertical axis. Not scientific, just my impression. I left it installed because the install was a hassle. Didn't remove anything else other than the bracket bolts, but the clearance was tight reaching them from underneath the car. Plus, I think the rear is more important in terms of body roll.