With the most recent builds, the only noticeable difference between the Athlon II and Phenom II dies is the Level 3 cache on the Phenom II. This can make as much as a 20-30% performance improvement, clock for clock. Larger cache means that the processor can store computed results on die without having to request it from the main memory. The cache memory is also clocked at a much higher speed than the main memory.
The only difference between Athlon II and Phenom II is the L3 Cache (the Athlon has none) which makes 0-30% difference depending on the application. Also Most Phenoms are black edition which means the multiplier is unlocked which makes overclocking easyer. The A series Llano are Athlons built on the smaller 32nm process with the built in GPU. As far as performance from the benchmarks I have seen the A8-3850 has the same processing power as an Athlon II x4 running at 2.9GHz ie the smaller 32nm process does not seem to make a difference to the performance (as far as I can tell from bench,marks I have seen).