i believe that wendigos are better. because of there speed any hex bags that the witch places will be exterminated before they can take effect. also the wendigo would easily eat the witch because the witch would not be able to use a potion or cast a spell in time.
I have search for the information of wendigo in the internet. I have not much idea about it. However, i would like to give some of my opinion for this debate. In my point of view, it cannot be good in this case. As you mentioned before, witch would be destroyed but what would happened when these witches totally disappear? Obviously, wendigo turn to human, seeking human flesh.