I'd go with the Kawasaki as well.
Too many horror stories around about Briggs.
A friend has a Gravely ZT with 21hp Kawasaki. Over 1300 hours with nothing but spark plugs, air filters and oil changes. Neighbor has a JD tractor with Kawasaki horizontal shaft. Has run the holy hell out of it for at least ten years. At one time, he was mowing six and sometimes nine acres with it. AFAIK, it's never been in the shop.
I'm sure some people have had trouble with their Kawasaki's but how many complaints are there on here compared to complaints about Briggs?