The X3: Reunion results are very unusual as the overclocked E6300 was actually faster than the overclocked E6700, despite the later having a 630MHz clock advantage. The standard E6300 processor was significantly slower than the standard E6700 in the same test however.
The Quake 4 results were more what I was expecting to find, the overclocked E6300 just matches the standard E6700 performance wise. The overclocked E6700 is significantly faster at 1280x1024 though.
Just like Quake 4, the UT2004 results show the overclocked E6700 leading the way by quite a significant margin. In fact, at 1280x1024 the overclocked E6700 delivered 34% more performance than the overclocked E6300 processor. Clearly the 4MB L2 Cache of the E6700 processor came into play here. Finally, Prey is more graphics intense and as a result both overclocked Core 2 Duo processors delivered similar frame rates. Here the overclocked E6300 showed a significant edge against the default clocked E6700 however.