YZ125 or the KTM won everything I have seen. Most said the YZ and KTMs had the best usable power. If you are not racing then there are no "bad" '06 125s. Everything I have read said they were all really close and it boiled down to personal preference.
i just remember reading in a magazine a few years ago, the 06 ktm was making 37 horsepower, dang! i think anything that new compared to what you had is going to be more than satisfactory though, it boils down to whats your favorite color?