TIG Welder is the most versatile by a long way. An AC/DC Tig welding machine will weld virtually any weldable metal and you only need to change filler rods to weld different metals. It is also capable of producing excellent quality welds on all metals in terms of both strength, low defect rates, and cosmetic appearance.
It is also usually the best method for very thin materials and the ability to control current and filler deposition separately makes difficult welds like thick to thin achievable.
Virtually all TIG welding machines can also be used for stick welding.
MIG tends to be easier to learn and tends to be quicker and more efficient in production contexts and so it can be a better choice for repetitive operations, especially for general fabrication in mild steel.
For many people, the MIG welding machine will be the best all-around choice, especially if you are mostly working in mild steel. MIG welder Is also a one-handed process that tends to be an advantage on things like car repairs where you are often welding in awkward positions.
Having said that, in terms of end results TIG welding machine will do everything the MIG welding machine can and more so if you want to be able to do any welding job TIG welder is the way forward, albeit quite possibly slower and more expensive for some common jobs types.
Stick welders don’t really compete in overall versatility but do have a few specific advantages. They tend to be a lot cheaper than either TIG welder or MIG welding machines, are more portable, can be used in windy conditions, are more tolerant of dirty base metal and rods are the only consumable. So they do tend to be useful for things like agricultural and industrial maintenance where you need to take the welder to the work and may not always be welding in ideal conditions. Stick welding machines also tends to be good on heavy structural sections in terms of both productivity and running cost.
What is easiest to learn and use is somewhat contextual and some people take to some processes better than others. On average MIG welder is probably the easiest process to learn to a decent standard and is less dependent on technique in most situations as long as you have the knowledge to get the machine set up properly for the job in question.
As to what to get
- if you want maximum versatility then a TIG welder will cover pretty much everything.
- If you want to do car repair and general fabrication in mild steel then a cheap or mid-range MIG welder is probably the easiest and the best value for money
- MMA welding machine is definitely the cheapest option, it is a bit limited, especially for novices, but excellent for things like agricultural repairs