That's great comparison. For long haul to get most dependability for the dollar would you go old or new for dedicated mig machine.
No one can answer what’s best for you.
For me, I sold my miller 211. It was an 08 model big transformer non auto set. I purchased it new. It had issues that I personally didn’t like without a good solution. Those issues affected me, but depending on setup, may not affect someone else.
I took that money and got a Lincoln mp210, inverter machine. 2018 model. Multiprocess was big bonus but I usually only use it for mig.
Has a few more settings that helps dial in what I like in my setup. Makes it a better product for me personally. It has a few quirks also.
That said, it needs to be what is best for you. That includes your budget, intended usage, features, etc etc etc.
It’s a tool. Some people swear by snap on/matco/binford. Some people are happy with harbor freight/craftsman/kobalt.
Buy the one that fits your budget and checks off the most boxes as far as what you are looking for.
I’m hesitant in buying used machines that I don’t know the history off.
Some repairs can be costly, not only in parts but also in labor.
Some older machines have much better parts in them that are designed to last 30+ years.
Ex: 1998 model miller dynasty is a tank. 2012 model dynasty is a joke.
My best guess for you, is to buy the HF you titled the thread about. It’s clearly already on your mind and I guess it still has one year money back guarantee.
Buy it, try it. If you don’t like it, return it. Can’t do that with any other brand machine out there. It appears to be exact clone of the Lincoln mp210, but I can’t confirm what’s on the inside. It’s new and has a warranty.
Or spend $300 more on the Lincoln, buy it from a local supply store and get local face to face support for it.
I would hate to see you spend $1000 on a used machine, that has problems in a month that may cost you $500-$1000. Then you are out cash and a welder.