itch.io

64 is better, but you can only use it if your computer lets you. If like pretty old it might be a 32 bit computer. 

Like Hotpink said, 64 bit is better and faster, but it's not supported on older devices. For computers, 99.99999% of devices are 64bit. For phones, it's something like 90%. My old phone I had about a week ago was 32bit, for example, and my current phone is 64bit.

For basically everyone, the best way to do it is pick 64bit apps, and if they don't work, try 32.