iMac 11.1 will identify your hackintosh as a new iMac, MacPro 4.1 will identify your hackintosh as a Mac Pro.
If you do Mac Pro, you can get Mac Pro specific updates, vice versa with iMac. I chose Mac Pro, and getting the option to update sound, because 'real' Mac Pro's have sound issues atm.
It doesn't do anything except identify your pc as an iMac or Mac Pro.