A good welder is the one that is capable of controlling the amperage in tandem with the intensity of heat that is required in the welding process.
Amperage varies from one machine to the other. The larger the amperage, the more power output it generates.
A welder with low amperage will only allow you to do simple welding or minor jobs. Choosing a welder with higher amperage will do bulky work without overheating and much interruption.