Defo HF start mate, the scratch start ones are NFG IMHO!
I "nearly" became a coded welder many years ago!
Have done MMA, TIG, MIG (MAGS), Oxy/Acet, & Atomic Hydrogen.
Mild steel, structural steel work, pipes, other general steels, tool & die steel (with heat treat) water, oil & air herdening, stainless, dissimilar steels, cast iron, of a few kinds repair and surfacing, aluminium and some alloys, brass, copper and a few dissimilar joints over the years.
Can't recall ever welding lead, nor high magnesium alloys.
Most of it repair or modification welding, not done much manufacturing except for odd jobs, what I mean is I have not spent weeks welding up fabrications, rarely more than a couple of days on each job if it was a new build.
Can remember vaguely spending 14 days welding the same cast iron press tool!
Also done the arc gouging, oxy/acet (& propane) cutting & gouging, brazing, hard, silver & soft soldering on loads of materials including dissimilar stuff.
Only in the last few years did I ever come close to sub-arc though and that was when the customer tried out a replacement control panel I had made for their sub-arc machine!
Funnily enough, fixed 2 MIG sets today & had a look at a diesel welder/genny for a customer after I got let out of prison.