My current nearest Kubota dealer (biggest in north Texas, I guess, with several locations) also sells Scag ZTRs. The salesman told me, quite some time ago, that Kubota is best, if you want diesel engine, and Scag is best, if you want gasoline engine. Of course, since that's what he sells, you'd expect him to say that, but I also suspect he just might be right.
Or get a Scag with a Kubota engine......like this.......