If you were to take a Miller, Lincoln, HObart, ESAB, Thermal Dynamic, and any of the other brands like Crapsman etc, cover em all up and let a pro welder run a few beads, odds are he will be able to pick out the Lincolns and Millers and Hobarts from the others, just the way they initiate the arc, and lay a bead........
While they all may weld, there is a lot of differences in the shape of the beads and how they are put down with the various machines all due to their open voltage circuit and control.........
I view a welder as a one time purchase, and If I was intent enough to need and learn how to use a welder and have a need, I would go with a decent welder, that would leave All but the HObart, Miller and Lincolns out of the picture.
Lincoln IMHO is better than a MIller in ne respect especially if your dealing with the 175 amp range models. Miller machines automatically increase wire feed for you when you increase the heat setting........is this good.......yes and no.......When I want to increase feed, I want to be able to do it and ot have a machine decide it needs increasing.....as a lot of times you may need a bit more heat without any additional feed...........other than that they are basically the same. I do think the Lincoln is better at the lower range and getting a consistent running and looking bead over the miller machines.......HObart is on par with the Miller, but does not quite lay a bead as nice as a MIller, but its still a certainly nice machine......
The biggest complaint I have with a Lincoln is the gun itself, as the triggers are extremely sensitive.......
What ever machine you get make sure its not hot until you pull the trigger......one that is hot all the time is a pain in the backside to use and can get you in trouble sometimes,
I would definately stay with a machine that is a 220 machine in regards to input voltage...........and also get one that is both flux core and gas capable.
While the machines that operate of 115 may work, and they do work good, they leave a lot to be desired, and sooner or later you will wish you wnet the extra $$ for more amperage. Stay with a Lincoln or Miller and you won't regret it further down the road.
You can weld 10 inch thick with a 130 amp machine if you put your mind to it, it would just take a heap of passes, so any machine will just about weld anything it just boils dopwn to how easy and how long it will take, but the 175 class machine is more than capable of welding up most items on a race car with ease............I would go with a machine like Lincolns 175+ or Millers equivalent, as the infinite control is better overall once youy learn the machine than presets are......