Soil perc test is typically 1 ft x 3 ft, but could vary. For this, the KX008 would probably do it quicker. However, depending on what else you want to do with it, the answer can vary (as I mentioned above).
Specs on BH77
Specs on KX008
As you can see the
BH77 has almost 2 ft more reach and 50% more breakout bucket force.
For a job within the limits of the KX008, it is always going to perform better.
Digging rocks? BH. Digging a stump? BH. Need to get to a spot 500 yards away? BH (excavator travels at about 2 mph). The KX008 weights 2200 lbs, and even if the arm can grab something it wont take much to tilt or move the machine.
This isn’t a straight forward comparison. However for that soil perc hole if you are willing to shell out $15-20k then the KX008 is your machine.