I've only delt with the Exmarks. They leave a great cut and their very easy to work on. But like it was said earlier, you'll have to demo the two of them and choose from there. Only then will you find out what you like as far as type of cut, noise factor, or the amount of fuel used.
I know a cutter who has the Kubota Z6-23 Gas Engine 54" HD Deck 5" depth, the Hydraulic Lift with the height adjustment dial is nice, the tranny seems alittle complex, has the Hermetically Sealed, no belts to change just fluid change's, It cuts ok but nothing like a Exmark, Toro, or Scag....Mark's Mowing Service