Hi, I have a MacBook 32 bit and was wondering would the new MacBook 64-bit Core 2 Duo processors run Leopard faster just because they are 64-bit? Or is the advantage of having a 64-bit processor just because it can hold more RAM?
Depends...
If you need to calculate on 64 bit numbers a 64-bit CPU is faster, it (atleast AMDs) also have more registers which makes it possible for the CPU to store away data within itself instead of in RAM which is much slower, finally they may have made some other improvements aswell.
But you also may end up with bigger memory pointers and eventually data/(instructions?) which uses up precious cache memory so in some instances it might be slower.
Most people who game on PCs run 32-bit because 64-bit Windows doesn't work that great and there are no huge speed advantages anyway, most packages prebuilt for Solaris are 32-bit versions since noone bothers building 64-bit versions of stuff which doesn't need it or will severly benefit form it. Most people who run Linux and BSD probably stay away from 64-bit versions of their OSes aswell because flash, java, win32 codecs and similair things might not work in a 64-bit environment.
So no, you will probably not miss out a lot.
During WWDC 07 Steve demonstrated working with a image on a 32-bit and a 64-bit system, and the 64-bit one where much faster of course, but that was because the image where 4GB large and therefor couldn't be held in memory on the 32-bit machine so it had to use the disk a lot, no **** it becomes slower then.
But how often do you open images or use programs which needs 4GB of ram? And in that case you need to upgrade the machine anyway.
Edit: The real _NEED_ people will have for 64-bit machines however will most likely be because they need the ability to address more than 4GB of ram.