The difference is the memory has its clock faster for about
50 Mhz, its speed is 4-4.5 ns (The GTS is 5 ns) and the core
i thinks its a little faster too (Don´t know how much!)
The Hercules Pro comes clocked at 200 core/ 401 Mem. It will overclock to 235 core/ 475 mem with out a problem with standard cooling. Dont know how well the plain gf2 does overclocking.