Shoulders are really hard to protect... all a pad/armor can do is spread the impact force across a larger area. Since shoulders are inherently pretty pointy pads are better for stopping bruising etc but they're not going to help much with the bigger hits you can take when skiing. Your best bet is to build up the muscles around that area so the bones and connective shit up in there have more support when you land on it.
i've hurt my shoulder a few times this year already (dislocated a few weeks ago, bodyslammed the snow with it today and cant lift my arm above my head now). unforunately its a hard thing to protect. pads can prevent bruises and such, but they wont do much for dislocations, and huge impacts on the whole shoulder that result in larger injuries.
i would recommend pads but i have even fucked my shoulder up playing lacrosse and actually wearing full shoulder pads. they dont do much