The 6300 has lower power consumption and runs about $30 less right now on newegg so if gaming is all you're going to be doing, it might be the better option for you. The extra 2 cores will only help you out in more heavily threaded tasks.
Depends on what you want to with them. In my opinion I'd pick an fx-6300 for most stuff as it has 6 physical cpu cores compared to only two on the Pentium. It'll help a lot in multitasking when you're running many applications at the same time.
They'll perform about the same as long as you don't have any other demanding apps in the background. (for the pentium).
However there are a few games like Starcraft II and Skyrim where Intel cpus perform better. If you play any of these games you could get the pentium if you want. Otherwise I'd go for the fx-6300 as it should last quite a while.
here's a list of various game benchmarks comparing a few fx cpu's including the fx 6300 and the fx 8320. They're very similar. In other bench's the 8320 outperforms the 6300, so all around near the same price with the sale I'd opt for the 8320 at that price range.
The 6300 has lower power consumption and runs about $30 less right now on newegg so if gaming is all you're going to be doing, it might be the better option for you. The extra 2 cores will only help you out in more heavily threaded tasks.