hi there
I have two different folding shovels both from military surplus. One is a wooden handled job, where as the other is a Z shaped US three piece model.
The latter folds down small and can be packed in a rucksack, the wooden handled on fits down the tunnel on the pocket of my Alice pack. Both do a reasonable job... toilet duty, small digging jobs, leveling swims while fishing etc... None of the folders I've seen would deal with 'serious digging'.
There are Chinese wonder shovels, or German army models... they are bigger & heavier. At the end of the day if I need to do any 'serious digging' I don't use a folder, but a decent shovel or spade.
I keep the wooden handled one in the back of my 4x4 and it is a tool to help get me unstuck if needs be, not my first choice, but it is compact enough to be lodeged in the cargo net on the back door of the car and remain there. For winter I fix a decent shovel to my roofrack to help deal with snow.
cheers
Gareth