There's practically zero difference in performance terms between the two low-end Black Edition Phenom IIs. That's not surprising, since there's also little difference between the two architectures. The extra megahertz don't really give you anything but a small increase in the video encoding score – a score that's easily bettered by the quad-core Athlon II X4 620.

Video encoding performance
X264 v3 – FPS: higher is better
Phenom II 560BE – 10.9
Phenom II 550BE – 10.4

CPU rendering performance
Cinebench R11.5 – Index: bigger is better
Phenom II 560BE – 1.89
Phenom II 550BE – 1.89

DX10 gaming performance
Just Cause 2 – FPS: higher is better
Phenom II 560BE – 45
Phenom II 550BE – 45