I like Kohlers because the bucket design makes servicing the engines really easy .
It also hangs the oil filter down so it is easy to replace without spilling oil all over the mower & drive belts.
The hydraulic lifters mean no valve lash problems which is the most common "won't start" problem I see.
Now this is for the Courage Command series.
The engines I least like working on are the Kawakasi's .
If they were designed for use on a mower then he was a sadists with a warped sense of humour.
Impossible to access oil filter and impossible to change cleanly. Blower housing that takes an hour to remove because of impossible to access mounting bolts.
Take your tool box into the mower shop and do a pretend removal of the oil filter and blower housing.
You can see them all but you cant get a spannar to to any of them clean and undoing 6 bolts 1/6th of a turn at a time is a PIA
If you want to keep the engine for a long time these parts need to be removed every season.
I charge an extra hour on Kawakasi powered mowers.
Even worse are the Donaldson type air filters.
No need to fit them to the blower housing like they are and in fact they would work 200% better on a bracket high enough to remove the blower housing and connected with a short hose.