3DMark2001 doesn't give you all the specs accociated with a benchmark run; the graphics card could have been overclocked higher, the ram may have been set faster, the swapfile may have been better optimized, the motherboard drivers could have been different, or even the ambient temperature of the other person's room may have been significantly lower.
There are people who get good scores with Abit boards, Iwill boards, AOpen boards, Asus boards, and several other motherboard manufacturers. I wouldn't blanket judge a manufacturer by saying they're always behind another manufacturer when it comes to performance; judge on a board by board basis, and get many owners' opinions on their boards. Many Athlon owners swear by Abit boards, as many P3 owners swear by Asus boards.
I have an Abit board (VH6), and last time I checked I was the third highest P3 under 1Ghz + Radeon 32mbDDR combo. I'm at 3157 marks; top spot is 3203 with an Intel VC820 board (RDRAM), and second spot is a (IMHO questionable as to the authenticity) P3@770mhz with an Asus board at 3160 marks.
My motherboard/processor combo (mated with my old Rage Fury Maxx) also currently has the second highest Rage Fury Maxx score in 3DMark2000 (first place is held by an Epox 8kt3a).