Which computer company builds the best workstation???
Celeron is not slower just because of the FSB; it doesn't have any L2 cache. Most users only look at clock speed which is not the greatest gauge for performance and upgradeability.
Celeron has 0 L2, PII and PIII have 512k and 256 L2 Cache, respectively. The faster Xeons have only 256k L2 while the slower ones have up to 2M.
PIIIs are only up to 133MHz FSB.
P4 and the latest Pentium Xeons have 400MHz FSB.
P4 is uni-processor based.
Pentium Xeon can be dual-processors.
There are other Xeon processors that have up to 2M of L2 cache but currently running at slower clock frequencies and running slower FSBs but there are machines that are massively parallel with up to 16 of these processors.