</font><font color="blue" class="small">( are the kohler engines better than kawasaki )</font>
Personally, I've had good luck with Kohler and Briggs & Stratton. While I've not owned one myself, I know people who've had good luck with Kawasaki. I think my first choice would be Honda, but that may only be because I had such good luck with three Honda motorcycles and one scooter and have talked to several people who had Honda powered portable generators, air-compressors, and such. The only engines I've had trouble with and wouldn't want again are Tecumseh and Clinton, and both of those were long, long ago so my experience and opinion of them is probably not valid today.
Personally, for a riding lawnmower, there are other features that would influence me more than the brand of the engine. My last riding mower was a Craftsman with a Briggs engine and the only thing I didn't like about it was the fact that the hydrostatic transmission was controlled by a hand lever instead of foot pedals (personal preference only because one works as well as the other).
And my personal preference for a riding mower is the Cub Cadet primarily because it had the foot operated hydrostat that I liked, and perhaps more importantly, it was so easy to remove and re-install the mowing deck, with no tools at all, so I could lean it against a tree to clean the bottom, remove the blades to sharpen them, etc.