JD really seems to focus on ergonomics in design, and put things in good places. Like many companies (not Kubota so much though) they've been piecing out their components. If every country of origin had a different color, JD green would be JD rainbow. They do have stringent quality standards, but how much oversight those get, gets more difficult when you have dozens of vendors in different areas. I have a JD--it's been great. The Chinese, Mexican and Indian components seem to have held up as well as the Canadian, Japanese and US ones... the Spanish ones not so much.
I think Kubota tries to keep as much as possible under their umbrella, so the 'best bid' is Kubota. It was the singular point that I 'should'ved' about after purchase, but have had no regrets about the unit over time--to date the concern is unfounded. I understand outsourcing is the new American normal for large corporations--it does not stop my lamenting it.
I'm sure either would serve you well, but am surprised such a great ownership experience has left room for competition... producers hope your kind of experience creates a lifelong relationship. Good luck with the decision.