I'm currently using Linux Mint 32 bit mainly because it generally consumes less RAM and recognizes 100MB more RAM than the 64 bit version. I only have 4GB installed in my computer and I know that all systems don't use the full memory installed but a little bit less instead. For example, 4GB = 3,8GB in 32 bit systems. The problem is that all 64 bit Linux I tried recognize only 3,7GB. You can say the difference isn't that big but it is when you don't have a lot of RAM.
Is it the default for 64 bit architecture? Is there something I can do to change that?