For certain type of work TIG is required, like welding chrome moly for some racing organizations. Intricate work, like gunsmithing is also well suited to TIG. TIG is used by many auto restorers who prefer a more precise, perfect finish that requires little to no finish work. TIG is most similar to gas welding in technique, so if you've done oxy-fuel welding, TIG should be a natural transition. MIG is required by law and by insurance companies in many localities for structural repair of automotive frames. MIG is also much easier to learn and faster to weld. For doing other types of welding, like sheet metal, it can be a matter of personal preference. For an auto body repair shop or a novice welder, a MIG is a good, practical all-around welder.

Depends on what u are welding there is mig , tig, arc thay are all for there own specilast things mig anyone can use i call it a hot glue gun i could teach you in a day not verry good for penertretion and not verry strong welds with hard wire but is verry fast and can weld km ,s in a day where a tig takes a while to weld small sections but doesnt put as much heat into the metal and is mainly used for alloy stainless specialized procedurs with a verry strong weld but can take you years to master