The best pipeline welder machine is the one that best suits your needs. There are many factors to consider when choosing a welder, such as the type of metal you'll be welding, the thickness of the metal, and the power source. A gas-powered welder is a good choice if you're welding thin metals, such as sheet metal or tubing. If you're welding thicker metals, such as plate steel or cast iron, a propane- or diesel-powered welder will be more powerful and will have more features.