According to a review by HotHardware the new AMD Phenom 9950 BE is about 4% faster than the 9850 which puts it roughly on par with Intel's slowest quad-core processor - the Q6600 - which costs about $30 less and uses significantly less power.
Summarizing the performance of the Phenom X4 9950 Black Edition processor is a relatively easy matter. The Phenom X4 9950 is the fastest desktop CPU to be released by AMD to date. Due to its 2.6GHz core clock speed, the X4 9950 is roughly 4% faster than the X4 9850 across the board. In comparison to Intel's offerings, the Phenom X4 9950 is about on par with the Core 2 Quad Q6600, trading victories depending on the test. The new Phenom X4 9350e is a little harder to categorize. As expected, due to its relatively low clock speed, the X4 9350e finished behind AMD's other quad-core offerings. It was, however, faster than the higher-clock tri-core Phenom X3 8750 in most multi-threaded benchmarks. In single-threaded applications though, the X4 9350e's 2.0GHz core clock resulted in comparatively lower performance.