If you are only concerned with gentle hills or steep ones of short duration waxes may be enough but if you want to climb a couple thousand steep vertical feet, breaking trail, with a large pack on your pack you'll need skins. With skins on your skis you can go just about anywhere. Skis with skins are far more mobile than snowshoes. Developed thousands of years ago there is nothing better. If you don't believe me try waddling around on snowshoes and breaking trail with 60 pounds on your back uphill or herring-boning around with wax.
Mohair skins glide better.
Plastic fiber skins don't freeze over as easily. The more skin you have under your skis the more traction you get. If you have alpine width skis with skinny ski skins on them you will have significantly less traction. With kicker skins you get more glide. I would say that is what waxes are for.