My understanding is that for AMD systems it is very important to run cpu/ram in sync. However, you appear to have a Intel system. From what I read, running out of sync is not a problem with Intel systems. Hence, go with the higher FSB and run the 5:4 divider.
Benching it both ways for yourself is good suggestion too
MSI KT3 ULTRA-2 KT333
Maxtor 60GB ATA 133 7200RPM