Linux illiterate

Hi,

I'm not exactly new to Linux once about 6 or 7 years ago I bought a small laptop with Linux installed and by the way, still works perfectly. I have also long ago installed Ubuntu 11.10 in a Windows 7 machine and by the way, never used. The present case is that I have been using Windows for very specific reasons, that is, because of a personal work I was developing that required Windows environment to function. Got fed up because Windows gives me a feeling of being controlled and told what to do by my own Personal Computer. I have several computers and my last one is very powerful: Intel I7, 20GB RAM, NVidia GeForce GTX 580 and runs Windows 7. I have also an I3 Laptop, 6GB RAM, running Windows8. I have no commercial or business intentions, I use computers to learn and improve my technical abilities for no other reason than personal achievements and fun. I'm a total maniac on learning and doing things by myself, and I'm interested to be again the one in control of my machines. I don't really know if Ubuntu is the best release for me but I wish to be a Linux user. The Ubuntu I have is installed on a 32Bits Machine that can get a 64Bits OS. My other machines are 64Bits and the minimum amount of RAM I have installed is 4GB. The elder machines can have a maximum of 6GB and the newest 24GB. Should I keep Ubuntu? What is the last version? Should I upgrade the one I have (on a 32Bits machine with 4GB RAM)? What is the best for the newest (64Bits, I7, 20GB RAM)? Thanks.

PS: Got most of the answers myself and upgraded from 11.10 to 12.04. Tested. Working!