Esab is pretty widely distributed in the USA. I had a weldor work for me for a couple of years who was really really good at every process, had certs for em all. He ended up being a show demonstrator for ESAB, this would have been about 4 years ago, and he LOVED the new ESAB Rebel multiprocess machine. This was a guy who had spent years and years on Lincolns and Millers. So my guess is, if you get into the mid and high end ESABs currently sold, they are decent.
Kempii has very little market penetration in the USA, they mainly concentrate on large orders of big power supplies for factory robotic welders.
Theoretically you can buy Kempii mig and tig machines here, but I have never seen one in real life, and I have been hanging out in welding stores since about 1980.
Miller and Lincoln have a lock on the market in the US, so we dont see much else. Local distribution, parts, and service make a big difference. I know my shop is currently pretty much all Miller, although I have owned Lincoln, Hobart, Century, and some euro stuff at various points. If I have a problem, the local supplier has an outside salesman who will drive me a part in a couple of hours if its in stock, or I will get it by mail in a day or two.
This is unlikely with Kempii or Fronius or other euro brands. Possible but more difficult with ESAB.
My business depends on those machines working. Cant wait a week for air shipment of parts from europe.
That said, the people I know who have used Kempii and Fronius really like em.
They tend to be more modern, more electronic, and more expensive than what many US shops want, though. Welding machines are a pretty conservative market, and, 50 years on since my first experience with solid state welding machines, I still know people who will whine all day about how nothing beats transformers.
Kinda like if you insisted all your vehicles had a carb for each cylinder, that needed mechanical syncing.