I need advice about Guitar Hero software & controller compatibility for Wii?

If your friend has the Wii console, then you need to get the guitar specifically made for the Wii. Xbox and Playstation guitars won’t cut it due to the difference in wireless connection.

Thanks – that much I knew but do you know if there are different Wii guitar controllers for Guitar Hero 3 vs. Guitar Hero 4?

Ah, totally misread the question.
I don’t have the Wii, but I’m pretty sure any Wii guitar will be compatible with Guitar Hero 4.

yes there are differences we got guitar hero world tour for wii but had an old guitar hero guitar controller from the guitar hero aerosmith last year and there were a lot of features we could not use on world tour because of the difference in guitar function the world tour guitar has more buttons and features that are not available unless you get that specific guitar

You have to buy a guitar compatible for Wii and also compatible for World Tour..it should say on the box.