"Snow Leopard's across-the-board leap to 64-bits, from the kernel to all of its bundled apps, will do more than just make more memory available. It will also have a significant positive impact on performance system wide, even more than the same jump to 64-bits in Windows Vista. Here's why," by Prince McLean from AppleInsider.

To read more, go to his article - AppleInsider | Road to Snow Leopard: twice the RAM, half the price, 64-bits