Within each brand, it depends on the version of engine, and the specs used to build the engine. I've learned over the years that engines can come with cheap internal parts that will meet the specs of the corporate buyer, but not add anything to the quality or long-term life of the engine. I recall engines being built with bushings instead of bearings, plus bearings come in all range of quality.
So, getting a good read on a brand of engine, doesn't mean much. If each engine had one standard spec then over time, we would know which would last the longest.
I would opt for water cooled, rather than air cooled. But that is just a quirk that I have.
My neighbor had bad luck with a Briggs air cooled, but it was a result of mice making a nest in one side of the cylinder cover, overheating that cylinder and burning it out. Expensive to repair. Fault of the engine? Probably not. But the Briggs name took the fall.
Kawasaki's have been good to me in several Deere lawn tractors. But then I didn't have one that had the plastic cam gear (I think that was a problem) which caused Kawasaki to take a hit.
I think Kohler has improved its image recently, as has Briggs, but there were years where their cheap imitations hurt them a lot.
