Ive had computers with a variety of intel and AMD Chips, now depending on what chip from the companies (core solo/duo, Xeon, Viiv- Intel or Opteron, Sempron, Turion64/X2, Athlon 64/FX/X2- AMD). Now if you have or are running a server of course the view on the processors would once agian be different....
I have had my best experiences with AMD. Their chips run cooler for the most part and they are a little bit cheaper. Im not sure if all but most of their newer chips will only run at the speed required for what is currently being done, right now as i am typing this my Athlon64 is running at 984 Mhz, it can run at a maximum of 2.19 Ghz. It basically comes down to what you need it for, i.e. gaming, modeling, animating...... as well as your personal preference, but id have to reccomend AMD as a processor.
and most people have this opinion.....DONT use a celeron processor!
Here is a link to AMD Processor Pricing:
Processor Pricing effective october 30th 2006