I have a DK45SE HST, and after spending a couple hours a week cutting grass, I can't help but think that just 5 more hp might get the job done just a little quicker. I didn't read the specs, but I would imagine that 5 more hp might make the tractor go just a little faster. Even if it was just one mph, that saves alot of time running around, in the long run.
I don't know what specs are different, but I am a big fan of bigger tractors. My 45 has done literally TONS of gravel, shale, topsoil, moving excavating and filling. When I make the long runs, I wish it went faster. Other than getting from point a to b, the 45 has done the work it has needed to. And it did some work it probably shouldn't have tried.
I'm not a tractor expert, or even Kioti's #1 fan. I owned a 28hp, went to a 45, and now wish I would have gone to something around 55-60. I would love to run a giant batwing, but I don't think it would handle the abuse on really hot days or on top speed med gear in anything but low cut grass/field. I know for a fact it has a hard time handling wet field work with a six footer on it. have to go slower which equals too much time cutting the field.
Don't know if this helps or not, thought I'd give you one owner's thoughts. I know someone on here will tell me they run a 92' mower in high gear through 6' tall weeds and brush, but that isn't my experience.