Lacrosse shoulder pads look very similar to football pads when they are underneath the jersey, but they are very different. They are really much lighter and designed to absorb a lacrosse ball shot, and normal body and stick checking while allowing for freedom of movement and speed.
We recommend shoulder pads that have the bicep extensions that cover all the way down to the elbow pads. This gives excellent coverage for the frequent stick shots they are taken to the arms during both legal and illegal checking. You want a good quality shoulder pad that covers past the end of the shoulder on the sides and does not move around when tightened up.
As players get older they may choose to go with lighter less protective pads that allow more freedom of movement, but they will do so with the understanding that there is a level of pain that will come with that freedom and decision. For youth players we recommend covering them up, including the rib pads.