Single cylinder Briggs motors are having issues. Best to stick with Kawasaki , Kohler, and the Briggs PXi multi cylinder (considered one of their commercial motors).
I've had 2 Kawasaki twins on my ZTRs and happy with both.
The thing that I avoid is mediocre air filtration systems. If it doesn't have a canister type air filter (like a Donaldson), I'm not interested.
Everyone I know with Kohler engines have had major issues at surprisingly low hours. I’ve had zero issues with my Briggs Commercial Turf and my buddy has a Briggs Vanguard with no issues either. Both mowers have well over 200 hours at this point.
What are the issues, and are they more of a problem with the engines, or the users who don't service them?
Back in the day I badly mistreated the single cylinder Briggs on my old 2007 John Deere LA110, and it refused to die. I eventually gave the engine some TLC and gave the mower to my FIL. It's still running fine and is being used as a cart puller around my FIL's property.