The Yanmars you are discussing are direct injection engines where as the Kubotas are not. Indirect is cheaper, and slightly less efficient. Durability would be about equal except for what ever the builder puts into it to make it more or less. The Yanmar engines are definitely top stuff. Just passing that along. Not interested in educating the public on all the quibbles about direct injection. Just letting folks who know not miss out on this fact about Yanmar engines. I learned this on the trail of coming to understand my perkins, (great engine) on the Dexta, then on my dodge commins trucks as the years went by. When I started shopping for a new tractor after 20 years out of the market, I was a bit surprised that John Deere which still had my heart strings, and then Kubota which won my heart strings for a while, did not have direct injection. That indirect stuff went out with Old Navistar ford diesels I thought.
By accident I stumbled into a test drive of the Yanmar I now own and I instantly said nice tractor but was still on my way to buy a LS or Kubota but while haggling over price I got to researching the Yanmars and in particular the engine story played out. I decided I was not going to pass up such a well engineered tractor because of poor marketing. I don't buy color.
The engine is sweat, those planetary gears in the rear drive are strong and quiet, the loader is awesome. And I believe I saved a bunch of money because poor marketing was making an orphan out of it.
But I don't believe there are going to be many if any more orphans. Yanmar has a new line of tractors, with a world changer transmission in the line up( hydrostats will become a thing of the past except for lawn mowers) and won't be cheap.