difference beetween ranger 8 and "pipeliner" welders

I have the Miller Bobcat which is similar. The dealer told me that the engines on the larger machines are rebuildable, whereas the air-cooled engines are good for about 3000 hours in commercial use and are not rebuildable. Typically the whole unit is replaced. Of course, in residential use like mine, 3000 hours is a very long time. I believe that there is a difference in the welding power generated by the larger units as well - 4-pole vs. 2-pole, but I cannot explain it exactly. The larger units seem to have a higher welding arc voltage than the smaller ones - will make a difference if gouging is performed. So there may be some difference in the arcs, but a Ranger 8 should be able to weld pipe.