It is all a matter of taste. As you can see from this forum, this Intel vs. AMD debate is still going strong.
I prefer Intels over AMDs, but they are both great chips.
Get either an Intel P4 or an AMD Athlon.
If games, 3D rendering, CAD and/or movie making is on your list of things to do with your computer. Then stay away from Intel Celerons and AMD Durons and Thunderbirds. They are meant for non-stress applications, i.e. word processing, spreadsheets, surfing the 'net and the like.