No argument there.

AC/DC inverter TIG can weld whatever is weldable. It's not the fastest, but it is the most versatile. The stick function makes up the rest for things like welding cast iron or working with dirty metal.

A few thoughts for the machine shop: if you want to repair large (heavy section) aluminium mis-machined parts, lots of amps is great to have. Pulsed is handy for building up thin sections or outside edges without undercutting. It's also perfect for doing weird stuff like tonight I was welding all these 1/8" rods to the edge of 16gauge stainless without undercut. I can't really comment on thin aluminium, but I would imagine low starting amps would be critical for that, which I understand the 255ext excels at. I have an old 225LX (like the 250EX) which starts a little higher. Steel and to a larger degree stainless doesn't need many amps since you end up in multiple passes for anything really thick. I don't go over 130 very often.

Foot pedal is preferred by most for sit-down jobs, but personally I've moved away from it to the trigger for almost everything I do.