You have to remember that when cat came out with the d10,the 9 got smaller,thats an old 9 and im not sure of the horsepower but the komatsu 375a is pushing over 650 horse and thats derated for the alttitude.
The 9 didn't get smaller until Cat renumbered the upper end of the line when they changed the 10 to the 11N, the 9L to the 10N and the 8L to the 9N. The 375 is also rated at only 610 flywheel hp for the latest model, and there is no derate for altitude here since we're only at 1200 feet.
The 375 has more grunt than a 10, it also has more weight. What it lacks is speed, precise blade control due to being so damn nose heavy,a comfortable ride, and any degree of reliability once it has a few thousand hours on it. Our 375 is running in the low 50s for availability, and our 475 was in the mid 30s.
I've run circles around our 375 with a 10R. While he could push more in one pass, I was moving more material by simply having faster cycle times.