In most all the computer systems I've built through the past ten years, I've found hands down that the AMD systems ran not only more smoothly than the Intel systems I've worked with, but have also had a longer lifespan.
But, as stated above numerous times, technology changes fast today. Yes, today Intel offers the fastest processors available, but at a much higher premium cost than processors from AMD. In your normal day-to-day work you would not see a difference really in the speed performance in an Intel or AMD processor anyways, that really only shines in high performance gaming and the likes. To say you want to buy Intel just because you think it will run your applications faster is in many ways false: There are many factors that make things run faster or more smoothly, and a difference of a few Mhz on your processor will not be noticeable in much of anything. If you want your applications to load faster, you're better to buy faster hard drives and put them in a RAID 0, along with more memory.
For those interested, it is said that the newest AMD Phenom X4 II (45 nm fabrication) will be released for sale TODAY. These processors have had some early benchmarking that shows they are very capable and will be a real rival to Intel. However, that being said, these new processors really are designed for the best performance in the upcoming Socket AM3 motherboards, which should be released relatively soon such as March or April.
But just to give you a comparison, the lowest priced Intel quad-core processor (Core 2 Quad Q6600) is currently priced around $185.00, and the cheapest new Nehalem Core i7 processor is currently priced around $300.00, the flagship of AMD, the Phenom 9850 X4 processor is cheaper than the cheapest Intel at around $180.00.
And if you are really interested in the best deal,
here is the newest AMD processor to market TODAY, a 45 nm processor with stock clock speeds of 3 Ghz quad core, at the same price as Intel's cheapest Core i7 with clock speeds of 2.66 Ghz.
To end my rant (I do apologize!) it all really does come down to personal preference. But there are many reasons why top-brand names from Dell to HP to Alienware all began configuring AMD systems using the Phenom processors in addition to Intel processors: It's the most cost-effective system possible. I've never really been upset with an AMD system that I've worked with. But then again, there are many others that will also swear by their Intel systems.