Horses for courses.
Oxy-acetylene is quite versatile but difficult on sheet metal or on thick stuff.
Mig is good on sheet metal and up to maybe 1/4" but the welds aren't deep on heavy stuff.
Tig is good on tube and sheet metal but requires great skill.
Arc is good on 1/8" and above and makes a nice deep weld.

Most pro welders have all of the above and use them regularly to stay good. They can make it look easy. I have a 240v mig and a torch for heat and can stick things together, but it's not art. In most cases you are way further ahead to have a pro weld for you.

Jorg