Inverters used in a welder tend to be more electrically efficient. This means that you are likely to get more power out of the welder for less amperage input. This is useful if you are working using the standard home power outlet. Transformers, on the other hand, while still the basis for many Mig welders are heavier and require more power to run. This, however, would not be considered as a deal-breaker, inverter or transformers still deliver the same welding function.