Nice speed lochabar, what is your batch number? If you want to know which of the 2 settings is faster, do a superpi 32M run at each setting. The higher FSB setting may win out, but if its only a little better and it requires more voltage/heat etc, maybe the slightly lower setting would be better for 24/7. It's unlikely you would notice a small difference in your day to day use of the pc.

You may be better off running say 4.4GHz & DDR2-1174 CL5 if your ram can handle it at a safe voltage.