Downhill pipe line welders prefered the Lincoln Sa200 because the older ones had copper windings and the amperage never varied as the machine got hotter
A strictly DC generator
They were more precise and better suited for that type of welding
Mine I liked because I could easily have more of as digging arc and more of a smoother less aggressive arc for crowning out pipe welds. For a engine drive it also picked the RPM in a spit second
Ive ran Millers and they were just as good and as I tell anyone one of the nicest running/welding machines I ever owned was a air cooled 2 cylinder AE-AD Miller with the Onan flat head engine
You could max that at around 250 amps, it would run 5/32 7018 wire all day
I did X-ray joints with that machine