My wife is on her second Deere zero turn.  The first one was more of a consumer grade

We traded it for a commercial grade mower and are much happier with it

Well ... now that she has a season with it she is happier.  When I did it she thought I was nuts.  But after running the new one she sees my reasoning. It is built heavier, mows better, will finish the yard without having to stop and fill the gas tank, has a button to raise the deck, all around better machine.  I can't speak to the comparison to a Kubota, but just want to caution you that a generic question like Deere vs Kubota may not get good answers.

I am a big zero turn fan.  However, if I had a lot of hillside to mow I might go back to a tractor type.  With a zero turn you either are in good shape or you're at the bottom of the hill.  Our road ditch isn't that steep, but my wife gives me the opportunity to mow it. You don't want a zero turn on a hillside or bank if it is the least bit damp or slick. Oh, and when you start up a hill with one you are committed.  Turning around or especially going backwards is not an option you want to explore.

My first zero turn experience was Gramp's cone drive Dixon.  He thought it was great.  I though it was great he thought so.

When we moved to this house he insisted I bring his Dixon out and try it.  I'm mowing along the edge of the road ditch when the drive chain breaks on the left wheel. There is just one thing to do when that happens.  You better hang on because you don't have time to pray.  It is "Ditch, here I come".