Oh... That's a nice question, but truly speaking it's very difficult for me to point out key differences between these two accounts, as I'm still trading on the individual one and it fully meets my needs.
The only thing I know for sure - together with professional account you receive a dedicated personal manager, higher leverage and lower close-out level, plus increased fund insurance.
I don't exclude there is something more I can't physically analyze, but if you are striving for pro account, here you go, apply for it.