I am too lazy to do so now, but later on I am going to find more benchmarks which show that Phenom II is actually a decent competitor to the i3 once overclocked.
First of all, to my knowledge there is no current i3 CPU which can be overclocked (if I am misinformed, please correct me). Going by that fact, your i3 would be locked at 3.1GHz (with turbo boost going to some higher speed under load I guess).
Now, considering the fact that Zosma and Deneb Phenoms are *fairly* similar in performance at the same clock speeds, I am going to post an Anandtech benchmark which you could have searched for hours ago.
http://www.anandtech.com/bench/Product/289?vs=362
Okay, these are some benchmarks from the very site you yourself claim to be legitimate (I do as well, Anand is cool). What can we conclude from the many benchmarks shown?
1. At a higher clock speed, an old Deneb Phenom II has no trouble beating the i3 in nearly every single test, even though the i3 is light years ahead in the implemented technology and architecture (even I was surprised at how well the Phenom did in some instances).
2. A Phenom II has even greater overclocking potential and could probably go to 4.0GHz, but only if you get the C3 stepping (I believe there are no more C2s lying around, so you should be safe).
3. A 960T would have potential to unlock two additional cores. This, combined with a greater clock speed achieved via overclocking, would actually probably go near the i5 2400 on rare occasions. If you find the 960T for less money than an i3, it is a no-brainer.
4. The power consumption of the AMD chip is a lot higher - it's the downside of the aging technology, but if you can live with it, it is not that bad at all.
5. Gaming - I see the obvious advantage the i3 has in games, but I do not think it is enough to justify buying it over the Phenom II which does so good in everything else. The biggest difference I see is around 10 frames per second, and the minimum framerate is probably even closer to the i3. But 10 frames is the max you'll see. Everywhere else, it's a dead tie.
Forgive me if my lack of knowledge on the Zosma CPUs made this entire thing irrelevant. If the performance is really that different to old Denebs, then this whole thing I posted is invalid. Also, my apologies go to the OP for straying from the topic, but I hope this concludes the stupid argument about which side is better.
It is always your choice!