Which is better, a 64 bit machine or a 32 bit machine?

LEt me first tell you what is meant by 32bit or 64 bit machine. When we say 32/64 bit machine the word length in the machine is 32/64 bit. That means on one clock 32/64 bit data will go from one location to other , say from CPU to RAM or RAM to CPU. So the Speed of data transfer within computer is indicarted by weather 32/64 bit machine. Now it will be clear to you that 64 bit machine will be better in general. Yes you need to use 64 bit OS to optimise the performance.

64 bit is the answer to all your questions above but the compatibility issues still depends on your OS. This one will really help which one is better base from your computer's features. http://windows.microsoft.com/en-US/windows-vista/32-bit-and-64-bit-windows-frequently-asked-questions

64-bit or more bit much better than small bit, you could use compatible OS which supported those machine. I think Windows 7 can be used for 64-bit machine, 64-bit equal 512 byte for computer instruction.

Definitely 64bit is much faster than 32bit machine. Just be aware that you also have to use a 64bit OS, to be able to maximize it. Its also much better if you are graphics oriented user.