Everyone is always trying to get what they think is the best value so any response you would get will be of course purchasing servers with the best hardware, support, and lowest price.
If you want a breakdown on the market, in 2004 HP was leading with 32.6% (14.1% growth), Dell 20.5% (27.4% sales increase for the year), and IBM 18%. However that'd be skewed towards enterprises as I'd think white box sales would cut more into those percentages if you only accounted for hosting companies.
Brand between the three doesn't matter to me, support has never been a issue for me between either Dell or HP, hardware quality is acceptable across the board to me with expected failure rates (minimal), and price is definately always a factor based upon performance ratings.
Personally I've never cared for whitebox builds, or customer builds. At one time I was building my own servers buying servermicro equipment direct. Now I generally find I prefer the warranty and builds of servers from Dell vs ever bothering with building my own or white box.
I think the issue between a smaller vendor like say rackmountsetc and Dell is you'd probably get more one on one attention from a smaller vendor, a more efficient supply chain as I doubt they do JIT building, and better support. Some people don't like dealing with larger companies or prefer the value in that personal attention they can get with a smaller vendor, or not being tied into a specific model like for the next 3 years.
As few here on the boards say, different strokes for different folks.
Are you trying to decide on your purchasing and equipment strategy, or just get a feel for what other hosts are doing?
We like Dell for their Dual Xeon. It's all because of their prices though. We have experience with HP and IBM as well. I would have to say they're all about the same quality (probably OEM from around the same place on earth). If you want the best quality Opteron, you should look at Sun. They're expensive, but their servers are one of the nicest we seen.
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