When asked which welding method offers the most versatility for the lowest cost, the answer is usually some form of MIG welding. The emergence of inverter technology means many MIG machines these days also MMA and DC TIG functionality. On balance, MIG welding offers the best balance between speed and quality.
There are some applications that rule out MIG welding completely. If you exclusively work outdoors, MIG welding can be challenging. MIG requires a continuous supply of shielding gas and a reasonably large setup that must be well planned to replicate in a portable structure. MIG is generally designed to work with a permanent system in an indoor environment. The advantages of MIG over TIG and MMA are briefly discussed here.
MIG vs. TIG
The primary advantage of MIG here is the large difference in cost. Yet a case may be made for cheaper TIG welders that only offer DC output. However, that also means that a lot of the functionality and versatility of TIG is being left out. A TIG welder truly shines only when it has AC output and the ability to work efficiently with metals like aluminium and to do finer finesse work. If you work with iron and steel, there is little need to switch to TIG. Upgrading to TIG also means learning new skills which can be fairly demanding. In particular, the need to feed a filler rod with your hand is very difficult to master, considering you may also be controlling the output with a foot pedal. It is important to remember that TIG skills are great if you have the time to learn them and the money to invest in a good AC DC TIG welder. If you are on a tight budget, it would be a good idea to set it as an eventual goal to work towards.
MIG vs. MMA
MMA or stick welding is versatile, can be done anywhere, needs very little setup, and one does not have to be too skilled. Visually MMA, or Stick, welds are generaly less professional looking. When welding sheets edge-to-edge, the joints can be weak as well. In comparison, MIG produces clean welds are strong with very little or no splatter. It produces almost no fumes. The biggest advantage MIG has over MMA is the amount of time you can actually spend doing your work. MIG welders have high duty cycles that allow continuous operation unlike the start-stop stutter required in MMA welding. You also have considerably less downtime as you do not have to reattach an electrode every few minutes.