Intel is superior in all the recent benchmarks (even with the new Phenom II out)
For gaming a dual-core is ideal since most games are not multi-threaded, but a quad running at 3.5Ghz will have the same performance as a dual-core at 3.5Ghz. I say a dual-core is ideal because they can overclock sufficiently better than a quad, therefore yielding greater performance. However, you would see the best performance in video editing if you purchased a quad core, but a dual-core at high frequencies and plenty of cache will get the job done.
I don't recommend AMD, I've had issues with the RAM frequencies when overclocking the 5400+. If I were you, I'd stick to the E7/8xxx series, get a good heatsink, and overclock it to 3.5-4.0Ghz. The performance outdoes the price in a large margin, in my opinion.