I have scrapped gobs of snow off my clients' skis when rentals forgot to wax the night before. Without scrapping the stuck snow off and rubbing on some wax, the skis do not slide at all. I can surely assert that --
YOU NEED WAX ON YOUR SKIS.
In fact --
EVERYONE NEEDS SHOULD HAVE SOME WAX ON THEIR SKIS ALL THE TIME AND WILL NOTICE THE DIFFERENCE BETWEEN SOME WAX AND A COMPLETELY DRY SKI
Having said that, I believe that if you are not seriously racing and the temperature is between 5F and 40F --
IT DOES NOT MAKE ONE LICK OF A DIFFERENCE WHAT KIND OF WAX YOU HAVE ON YOUR SKIS.