Evening all! What’s the general consensus on wind deflectors? Just on the front windows or on all four?

Hi ALL, Newbie here with our first MERC and its is A180 Blue Efficiency 2013 model W176. Bought the car about 2 weeks ago, I did not get to test the passenger window switches and I was informed they worked perfectly before buying it. Anyway, be that as it may. The passenger front window...