I guess I'm going to feed a troll...
Why do you want to upgrade? The difference between the two is almost nil.
Because Microsoft committed fraud. The EULA for Microsoft Windows 7 Home Premium says that I can run it on 2 physical processors in one machine, but in practice it only recognizes one Intel Xeon processor in my Dell Precision T7400. Therefore, I need to upgrade to Windows 7 Professional to get the functionality I was previously promised by Microsoft in a written contract.