ok , interestingly enough, the difference is in the chipset. although both boards use the nforce2 ultra 400 chipset, the Pro uses the MCP-T southbridge, while the Pro2 only uses the MCP southbridge. go figure...you'd think it would be the other way around. i think what Gigabyte originally intended when they created the Pro2 was to take an already moderately priced mobo (the Pro) and make it even cheaper by utilizing the more cost-efficient MCP southbridge. ironically they seem to be selling for the same price at newegg. anyways, to read up on the actual differences between the MCP and MCP-T, check out AnandTech's
NVIDIA nForce2 Preview. so essentially the Pro is better because its southbridge contains more integrated features, and do you really need to get the Pro2 when the Pro can be had at the same price?