Hi,
Do you have a 133MHz FSC Processor ?
If not, then take the PC1600, because, the mem bandwith don't helps to much, if you can not get it to the processor!
Do you have any closer spec to the DIMMs?
Normally, the PC2100 will run as 2.5-3-3, and I expect the PC1600 to run as 2-2-2. Therefore...