If you have physical problems (or are concerned you may develop physical problems from snow shovelling), the best snow shovel for you to buy may be one of the ergonomic snow shovels.
Beyond that, determining the best snow shovel to buy largely comes down to weighing your needs (i.e., how you will be using the snow shovel) and preferences. Will you be using the snow shovel to chop ice, for example? Snow shovels that are made to be lightweight (including aluminum snow shovels) don't hold up well to ice-chopping. But do you want to be lugging around a heavier snow shovel, something that will stand up to ice-chopping? Probably not. My preference is simply to keep an ice chopper on hand, thereby saving wear and tear on my regular, lightweight snow shovels (I use both plastic and aluminum snow shovels).