I bought a Land Pride SA20 ssqa post hole digger with the low flow motor. The low flow model requires 1500-3500 psi and 6-15 gpm flow. Medium flow motor needs 10-20gpm, and high flow 15-30gpm.
My Kubota
L4060 is 9.4gpm total flow and the auger works fine, but it's slower in rpms compared to my previous PTO driver auger. The only disadvantage to the slower speed is that it doesn't sling dirt out of the hole like I'm used to. What worked best for me was stopping the auger 2 or 3 times and lifting the auger loaded with dirt out of the hole. Not really a big deal, just different.
On the BIG plus side, having down pressure made the work a breeze. I have a lot of chunk concrete from a demolished set of silos on my property. Without down pressure I was busting and removing small chunks by hand in almost every hole. With the new auger it either busted it up, or moved the concrete chunks into the vanes and out of the hole. I only had to pick one piece out of one hole that just refused to come out with the auger.