Who wouldn't it be a good idea?
64bit Windows is generally faster than 32bit Windows, especially if you have a few native 64bit applications that you use regularly. The 64bit version of Handbrake garners a 15% performance boost over the 32bit version, and even the 64bit version of office apps like Excel experience a notable speedup when the native 64bit version is installed.
64bit Windows is also more secure then 32bit Windows. One of the biggest security improvements comes from Kernel Patch Protection, which is only available on 64bit Windows and seriously hardens the system against things like rootkits. 64bit Windows also enforces signed drivers, while 32bit Windows doesn't. 64bit Windows has much more effective ASLR (Address Space Layout Randomization) because it has an virtual address space to randomize within in WAY larger on 64bit than it is on 32bit.
Unless you have some piece of legacy hardware that needs an old unsigned driver, or legacy software than needs 16bit support... why on earth would you ever pick 32bit Windows over 64bit Windows?
2GB of RAM is already pushing the lower limits of comfortable multitasking, and despite all of the above in general most/many apps you launch will use more of your RAM due to (paraphrasing) 32-bit to 64-bit translation/overhead. To top it off, 2GB is the minimum required for 64-bit as compared to 1GB for 32-bit, so that says something to.
Regardless, the fact that some of the drivers are 32-bit only is a good reason too.