This question is one that is deeply rooted in technology and one that could easily take more space than is available in this column, but here is my digest version.
In the computer world, bottlenecks are what cause those performance delays that we all detest and anything that can reduce the bottlenecks can improve performance.
In simple terms, the data path on a 32-bit operating system is half the size of 64-bit operating systems. That means that your computer can be slogging twice as much data around at any given time with a 64-bit OS.
Think 32-lane highway vs 64-lane highway: twice as much traffic can use the highway at any given time.
In the computer world, however, in order to take full advantage of the 64 lanes you need specially designated cars that are capable of using the extra lanes. Think of the extra lanes as only available for car pool vehicles that run on alternative fuels that are the color green.
In order for a 64-bit version of Windows to be of value to you, you will also need a 64-bit processor and 64-bit versions of the software that you plan to run. Without all three, you would be wasting your time.
Additionally, the 64-bit version of Windows can run faster because it can address more physical memory (generally referred to as RAM - Random Access Memory) and avoid using the much slower hard drive for active memory needs.
The 32-bit limitation for RAM access is @ 4 GB which means as soon as Windows needs more working memory it has to swap out information in temporary free space created on the hard drive (referred to as the swap file) and this is only if you have that much RAM installed.
Since most of us have much less than 4 GB of RAM, we are using the hard drive much more often for working memory, which is why we often find ourselves waiting for the computer to respond to our requests (meanwhile the hard drive light is flashing almost solid).
To really make things zing on a 64-bit system, you would want to install huge amounts of RAM (8GB or more) and again, only if your software programs can address this additional memory.
While all of this sounds like exactly what we have all been waiting for (both Linux and the MacOS have been 64-bit for many years), the reality in today’s computing environment is that you will be more likely to suffer from the compatibility issues that have always plagued the 64-bit Windows world than benefit from the advancements that it provides.
Unless you are building a computer that is specifically designed to run a special application such as 3D modeling, video gaming or work with massive amounts of data AND you have the discipline to only install applications that have been written as 64-bit programs or you do the research to ensure that whatever you install including your printer, scanner or digital camera software will not cause a problem on 64-bit Windows versions, your likely better off sticking to the 32-bit version that provides less headaches.