Welding services providers have four main options at their disposal when they want to tackle jobs. Before you start a welding project, it's a good idea to understand each one and their pros and cons.
The MIG welder is the simplest of the options available, and consequently, it's the one that serves as the workhorse for many shops. MIG systems employ electrodes to generate the necessary heat for feeding the material. This produces aesthetically pleasing and precise welds, and that makes it popular for jobs where welds will be visible, including everything from art to architectural features.
On the downside, MIG welding is less than ideal for high-strength applications. You won't be using it with cast iron, and it also can be too strong for use with aluminum. MIG processes also require extremely clean conditions and materials, and that makes it unpopular for applications in difficult environments.
A TIG welder uses a torch to assist in the application process. It's a very clean process that's capable of greater precision than MIG systems deliver.
TIG welding isn't great for use with thicker materials. It's ideal for use on nearly all metals, except cast iron. If you're trying to do something simple and clean, such as fixing a metal basin, the results will look great. TIG welding is less practical for heavier projects.
This is the simplest process, but it also requires the greatest amount of individual skill. Stick welds are generally very strong, but producing clean work is all about the talents of the person doing the work. An electrode supplies heat, and flux is directly applied rather than being piped through a gun. It's not ideal for use on thin materials, though.
The main appeal of stick welding is that it handles ugly jobs well. An old joke among welders is that "you can't weld air," referring to when something is so rusted and janky that you basically have nothing to work with. When the job is bad enough that you're basically welding air, the stick welder is the go-to tool for making the impossible happen.
This is the preferred process for doing work on heavy equipment. It also is frequently employed in construction work. Arc welding should only be used on thick materials that can stand lots and lots of heat without being burned through. It's a very efficient process, and skilled professionals do work arc work that requires little clean-up.