For the record, AMD says that a single Bulldozer module has around 80 per cent of the performance of two conventional CPU cores. In other words, a four-module Bulldozer core should be at least as quick as a six-core processor.
That being said, the 6100 is a 3-module, 6-core cpu. 6*80% = 4.8 true cpu performance. The issue is in light threaded applications, you still take the 20% hit, so the phenom II comes out slightly ahead.
So the real question is will the game you plan on playing use 6 cores or only 4. Most games only use 4 cores, but the newer games are becoming core friendly (BF3, Civ V, Dirt 3, ect)
IMO, $30 isn't worth the difference for a few games, go with the cheaper Phenom II. If they were the same price, flip a coin.