Mechanically, it's a wash. Neither is a clear winner from the "design" perspective. Some will swear by the DOHC Honda, others by the Kawasaki. No clear winner, IMO.
Esthetically, that's up to you. The Honda C is a 'Custom' with stepped seat, shorty mufflers and pull-back bar. Maybe you like that, maybe you don't. I don't know what the KZ-E style is - cruiser? standard?
The overwhelming decision-maker will be the condition of the specific bikes you're looking at rather than any model-inherent strengths or weaknesses. Which one looks nicest? Which one seems to have been maintained better? Which one runs, goes, stops best? Any 'extras' with one of 'em? Standard used-bike questions....
Good luck, and post back which one you end up with.
Kirk