If I were given the choice of using either a low power/budget hoby MIG or half decent hoby MMA welder, personaly I would go for using the good ole stick.
I would use 2mm thick chassis tubes, most importantly, use the right electrode for the job ( Some are better suited than others )
Go to a welding supplier that knows what they are talking about & ask them to recommend a good general purpose Rutile welding electrode for the welding of thin material
If the fancy took me, I would use a stick welder in the blink of an eye, that said, I have been trained to do so
