Brianle
Its all about avolanche. If you have to dig someone out you will want a tough metal blade, not a whimpy metal or plastic blade, but without avo transcievers it also doesn't matter since you won't know where to dig anyway.

If you do not camp in avolanche country a plastic shovel is just as good (almost), BUT - what actually will you do with a shovel? Dig a cathole? A shovel may be just wasted weight unless you PLAN on digging. Fill your pan with snow to melt? Both? . I always carried a plastic bladed shovel in the Sierras, then a snowclaw which is totally worthless, and now I just use a ski tip for camp chores.

It takes a lot less energy to carry and pitch a tent than to carry a shovel and dig a cave, and you will be dryer with the tent.
Jim