If you're looking for the flywheel weight, find the specifications and compare the total weight of each engine. I do not know how the honda and kohler engines compare, but my suggestion is to go for a commercial/industrial grade engine. They tend to be much more durable (and heavier in weight).
I have a '76 Horse tiller with the original 7hp Kohler. I think they are much better built than the new ones, so finding a good engine is worth it