Maybe these welders are tuned with Aristrorod, it's the one ESAB product that is made in China.

It's funny, where I used to work we had an ESAB that ran best on Hobart wire, and a Hobart that was best with ESAB SpoolArc 86. The machines were used for different jobs, but I always thought that was odd. If you swapped wires, neither machine worked as well. I was told at the time it had to do with the inductance of the machines as these did not have all the bells and whistles of modern MIG welders.