i think i read somewhere that in real world testing pc3200 has a performance increase of 7-15% over pc2700. i would get whatever is cheaper unless they both cost about the same, in that case get pc3200.
what CPU is it? you may be able to set that 333fsb cpu to 400fsb and just decrese the multiplier. cpu and mobo fsb should be the same to maximize performance.
for example with XP2500 which run at 333 you can easily overclock them by setting fsb from 333 to 400 using the retail version which come with a heatsink/fan. you would end up with an XP3200.
or if you didn't want to overclock it but wanted to increase front side bus to 400 than set the multiplier, from i beleive, 11.5 or 11 to 9. you would end up with an XP2500 still but fsb would be now 400.
lots of people who bought the XP2500 barton ($92 retail version) have confirmed this. it may be possible to do that with other XP 333fsb CPU's