I know I shouldn't say anything but at this point in time only an idiot would buy a dual core processor if they could only afford 1 processor for 1 machine. I found dual cores almost useless for gaming and other things years ago. but there are those that still insist they're not irrelevant. only way I would toss one in a machine is if i knew that in very short order i was going to dump it for a quad core............. not have aspirations but actually going to do it. in that case I would buy the cheapest one i could.
Notice how in most tasks the X4 wins . . . and in pretty much every single game the i3 wins? They didn't have an i3-3220 in the test, but it should be just about 10% faster than the 2100 in the example. Putting it well in the lead, even in MMO games.
So if the machine is primarily for gaming, the i3. If the machine is primarily for stuff, the X4. If you want the best of both worlds, save an extra 100 bucks and get an i5.
Factors to consider, the Phenom II's K architecture is really old, basically AMD flogged it for to long but the upside is for its time it was a mighty efficient chip and at a good price point. Today it still is a good processor but it has been effectively replaced.
The Core I architecture is much newer and more power/performance efficient but that is at times a very overrated factor when it comes to gaming rigs. While I am sure there will be a bazillion and one synthetics out showing the i3 to be the most amazing gift to planet earth, frankly there really is nothing decernably different.
On this one, the i3 will run cooler and efficient but you are basically rocking a retro dual core with a last hoorah.