Is there a big difference between these two types of RAM? As long as the
mobo can support it?

PC 2700 is 333MHz, PC 3200 is 400 MHz. So, whether you will get any
performance increase using PC3200 depends on the FSB of your processor and
motherboard support. If your motherboard will support 400 MHz FSB, but your
processor runs at 333 MHz (2 X 166), then there isn't really any advantage
to running faster memory. This assumes you're not overclocking. I'm
referring to AMD systems...others can address Intel better than I.

Fitz