My personal experience has been that you use what you want. I have had both AMD and Intel machines.
On a desktop side, it comes to how much you want to spend. Intels have the performance edge if you spend the big bucks. If you get down to desktop processors that are budget processors that perform well, I would go AMD. The minuscule difference in performance may only matter to someone trying to cure cancer in the next five minutes.
On a laptop Intel has the edge there. A laptop was designed to be portable and useable for a workday (6-8 hours.) My own netbook, ASUS EeePC 1000H, is one such device. It handles nearly anything I can throw at it, and stil gives my just shy of 6 hours of battery life. Now, I Must say AMD has made strides in this are with their recent chips. The NEO X2 Platform definitely is catching my eye.
So it is really all up to preference. For now, keep an eye on the news and when that killer x(number) core processor comes out, run and buy one and have fun. There are a ton of good articles online for building a computer for any budget, google it and see what you find.