Stick with the OS. While SOME guys have mastered the K&B's...the vast majority of guys out there who have tried them have had the unpleasant experience of examining the gliding capabilities of thier jets with them.
Ask around, and you will find an OVERWHELMING majority will prefer the OS91.
In the long run, it's a lot cheaper to buy the more expensive OS than it is to trash an airplane when the K&B cuts at an inconvenient moment.