On paper, it looks like the Hustler wins. It's faster, has more fuel capacity, more horsepower, 6-way seat...
BUT--I've never heard of Shiabaura diesel engines. I've used and owned Kubota diesels since they were first imported so I know what you get with Kubota and I'm a big fan. Kubota is an established global manufacturer of ag equipment of all types whereas Hustler is a small Kansas company, I believe.
Having said that, if it was me that had to choose, I'd be biased in favor of the Kubota but I'd look very hard at the Hustler before I bought either one.