Not sure about TouchWiz or other varients of Android but on Sense you have two options...
1) Erase Phone Storage (which clearly explains that it is music, pictures, etc)
2) Factory Reset (erase phone data)
Seems pretty straight forward to me.
Also to me it makes sense to keep these things separate. My friend had to wipe his phone because it was randomly rebooting and it saved him from having to connect to a computer and backup all his music and photos.