Hmm, your title doesn't match up with your question... but let me just tell you a few things.
AMD CPUs tend to cost less, and all in all, the system will be slightly cheaper. AMD Phenom II X4 is roughly around the performance of an i5 760, although not quite. Clock for clock the i5 is faster, and both can OC to roughly the same frequency.
i7s aren't really needed for anyone who is only using their PC for gaming and other non CPU intensive tasks like web browsing. If you might be doing a lot of rendering or audio and video editing then it might help to have hyperthreading on your quad core, but everything from the CPU to the motherboard and triple channel RAM will cost extra compared to i5s and Phenoms. The only legitimate reason for a gamer to get an i7 is for quadfire or quad SLI GPUs, or in rare cases a lot of peripheral cards that need high bandwidth. The i5 (P55 with 16 lanes) is equal to the i7 (X58 with 32 lanes) on current gen GPUs up to 2 cards in all cases and up to 3 cards with NF200 chipset mobos.
However, Intel just released Sandy Bridge which is slightly faster, clock for clock, than the last gen i cores. This means a stock i5 760 is slower than a stock i5 2500, and prices should be pretty close. If you intend to OC, look at the i5 2500k which is "unlocked".
Anyway, in a nutshell AMD Phenom will be better bang for your buck if you're a gamer as it delivers adequate performance. They also have a 6 core CPU, which doesn't perform quite as well in gaming but it's better in rendering and such. Intel tho is still on top, but costs a little more.
Easy answer? None, AMD is more cheap and gives your very good performance for the money, but not at the same level of i3, i5 or i7. Even, with the Sandy upcoming, the prices of Intel will drop a little and that makes another positive point for Intel.
The AMD X6 barely competes with the i5-750 and it has 2 extra cores to help it take the win in a few categories. PhenomII x4 is equivalent to an I5-760 in pretty much an "only gaming" scenario.
If you do video encoding/transcoding Sandy Bridge is the way to go. Until Sandy Bridge actually hits the market and prices stabilize its hard to say which is the better value esp considering Microcenter has the i5-760 for $170.