We begin the synthetics with 3DMark Vantage:
Indeed, the stock Athlon II X3 435 looks to perform very closely to the Phenom II X3 720. This synthetic benchmark is multithreaded, so the Athlon II X4 620 shows its quad core strength, although when overclocked to 3.77 GHz the Athlon II X3 435 takes the lead.
PCMark's system score doesn't care much for shared cache, but its productivity benchmark seems to take L3 cache into account.
SiSoft Sandra seems to respond to clock speed and the number of CPU cores rather than L3 cache.
The synthetic benchmarks seem to favor the Athlon II X3 435 as a viable alternative to the more expensive Phenom II X3 720 Black Edition. Let's see if the actual application benchmarks bear this out.