Why might my choice in CPU's change if I were to build a computer system for encoding DivX home movies instead of for gaming?
I also smell a homework question. I'll give you a little bit of a hint without completely giving away the answer. Those are very different kinds of tasks. If you want a hint, look at benchmarks here on Tom's and note how well the various Intel and AMD CPUs that are all near the middle of the list on one benchmark fare in other benchmarks. That will give you a clue as to what applications demand what features from what CPUs.