In Macbook Pro 17", what's the difference between processors?
2.5 GHz (2860QM)

2.5GHz base clock, 3.6GHz max TurboBoost clock.
8MB cache.
Bus/core ratio: 25.

2.4 GHz (2760QM) 

2.4GHz base clock, 3.5GHz max TurboBoost clock.
6MB cache.
Bus/core ratio: 24.



You can compare the features side-by-side here.

The actual difference is 4x0.1 GHz. 

The links will tell you that there is no difference besides the clock speed, cache and bus/core ratio. Exactly the same specifications for advanced technologies, memory and expansions.

According to this source there is a 5.2% difference in performance. 7987 vs 7592 with PassMark.