I am a Deere guy, but I really like Kubotas. I think Deere currently beats Kubota hands down in ergonomics. But I bet Neil is excited to hear about new products (I know I am...). I like the newest Kubota designs and bet the new one's will continue the trend. I really am making myself sick, cause I really do love razzing ol' Neil. Don't tell HIM but even a Kubota will make you proud!
One major diff is that the Deere is Turbo. If you are elevation, that is the ONLY way to go. At sea level, the advantages are as profound, but still may lean to the Turbo engine. One note, All 4000TWENTYs share the same componants throughout, with the exception of some fuel delivery items. A 4320 ought to be loafing, as it is almost a 4720 just 'coasting'.
That said, I dunno that I would like the 4000's Deere engine as well as my Yanmar or a 'Bota.