This is based on my experience as network manager for an institution with 500+ PCs.....
My story About 3 years ago I bought a load of 'cheap-but-good' Athlon 2000+ PCs and a load of intel celeron 2.4 machines with intel branded motherboard, which cost ~20% more...
Performance-wise, there is very little difference, at least with Win XP, Office 2k3 and the usual workstation apps. This makes a farily clear argument for AMD however...
Both these sets of PCs are now out of warranty, and when I bought them I expected them to last 5 years. In the first year (in warranty):
about 20% of the AMDs died, and were replaced with new non-identical bits (whatever was current at the time), which generally meant an entire rebuild rather than simple cloning (few hours work)
about 15% of the intels died. I got identical parts to replace them. No problem with cloning, drivers etc. (plus intel motherboard driver support is really easy to use).
3 years down the line, I can still get identical parts for the intels off ebay. However, you try to find L7VMM2 motherboards on ebay - I have a notification on these, and have not seen one for 6 months. As a result I still have 100% of the intels running, but only about 60% of the Athlons
The bottom line:
you want a cheap ast PC and like reinstalling windows and getting frustrated wth blue screens and bankrupt suppliers, then AMD is for you
You want something that will give the minimum of fuss for the next 6 years, buy intel