Okay, as you can see, I'm reasonably new at MDing but I have been putting in time and from a digging stand point here's my few cents worth . . .
I'm located in northern Illinois and our ground this year is REALLY dry!! Dry and hard! For my "digger" I use a simple aluminum planter tool, about 11" long X 2" wide with a very comfortable cushioned handle. It has inches etched along the blade part and was bought at Home Depot for about $6-$7, I don't recall. If one breaks this I would suggest cutting back on the arm & hand exercises.
Because the ground is so dry and hard I assist my efforts by using a decent size screwdriver and I stick it in the ground around the target area and pry with it just enough to break the ground up a tad. Then I dig the rest (it's almost dust) out with the digger.
When the ground is a little bit wetter I use a not quite decent (Kellyco supplied free with my MD) knife and cut around three sides of the target area and then slightly pry with it (This knife WILL bend!

) and then remove the knife and dig the plug with my digger.
Note to myself: Get a better knife!!
In moist soil I have stuck this digger in the ground as far as 3-4 inches on my first go at it and pried an unassisted (no screwdriver or knife) plug out of the ground without any bending at all and I just have to doubt that I could, under reasonable pressure, break this digger.
I suspect we all have our favorite tools as we do MD's but I think some of the specialty tools are a bit over priced for what you get and can be replaced with better, cheaper tools at local stores. Of course OMHO.
Hobo