The best backpacking shovel is not something you would use to dig a foxhole. All you need is something to cover your campfire, something to use to dig a small hole for a single or 2 person latrine and something to scratch out a small channel around your tent when it rains. The idea here is small, strong and light weight.
You are not going to be fighting fires with a backpacking shovel but if you are fighting fires you already have a much larger shovel so you will not need a small one to dig a hole to go in.
The perfect backpacking shovel would be light weight and strong enough to dig through small roots. I use a plastic camping trowel. I found one made of a composite material with serrated edges and is ideal for digging through small roots. It is strong enough to scrape out a channel in gravel and it is light weight ( 2 - 3 Oz.). I carry it in an outside pocket of my pack so it is easily accessible if I need it on the trail. And I don't have to worry about dirt getting into the inside of my pack.
I have seen some made of aluminum or stainless steel but they are heavier. Many manufacturers claim to have the best backpacking shoverl but steel shovels rust and some plastic shovels are too flimsyand without a serrated edge.