It depends on the two setups.
PC2100 is running at 133MHZ DDR, while PC2700 is at 166MHz DDR. So in this setup 166MHz is faster than 133MHz.
However, When you add in the latencies, A.K.A., CAS, RAS, etc; the overall speed could be slower eve though the fill and empting speed is faster.
I.E. PC2700 2-3-3 vs PC2100 3-2-2
The PC2100 has less latency and will most likely be faster by .5 to 1.5 ns. (ns = Nanoseconds)
Get some specs on the memory you are looking at and we on the forum can help you choice the best choice.
<b>All for one and one for all...and 3 for 5! - Curly - The Three Stooges</b> :lol: