Should I use Python 32bit or Python 64bit

Question

64 bit version will allow a single process to use more RAM than 32 bit, however you may find that the memory footprint doubles depending on what you are storing in RAM (Integers in particular).

For example if your app requires > 2GB of RAM, so you switch from 32bit to 64bit you may find that your app is now requiring > 4GB of RAM.

Check whether all of your 3rd party modules are available in 64 bit, otherwise it may be easier to stick to 32bit in the meantime

In my experience, using the 32-bit version is more trouble-free. Unless you are working on applications that make heavy use of memory (mostly scientific computing, that uses more than 2GB memory), you're better off with 32-bit versions because:

1. You generally use less memory.
2. You have less problems using COM (since you are on Windows).
3. If you have to load DLLs, they most probably are also 32-bit. Python 64-bit can't load 32-bit libraries without some heavy hacks running another Python, this time in 32-bit, and using IPC.
4. If you have to load DLLs that you compile yourself, you'll have to compile them to 64-bit, which is usually harder to do (specially if using MinGW on Windows).
5. If you ever use PyInstaller or py2exe, those tools will generate executables with the same bitness of your Python interpreter.

You do not need to use 64bit since windows will emulate 32bit programs using wow64. But using the native version (64bit) will give you more performance.

Use the 64 bit version only if you have to work with heavy amounts of data, in that scenario, the 64 bits performs better with the inconvenient that John La Rooy said; if not, stick with the 32 bits.