Does mig welders or arc welders make more money?

That all depends on what type of arc welding you are doing, Mig, Tig or MMA (stick)

It also depends on what standard you are working at, what you are welding, where you are welding and the level of danger you are in i.e. are you in a warzone, underwater, high up etc etc.

A typical basic mig welder the does tables and chairs etc can look to be earning about 12,500 to 15,000 pounds a year.

A fully coded welder working on high pressure steam lines etc can earn upwards of 52,000 pounds a year.

Then you can factor in danger money, are you working away from home, overtime etc and get even greater amounts.

I had my Asmi 9 which is one step below coding and was earning about 26,000 a year welding sonic cleaners, furnaces and wire winding machinery.

It all comes down to your skill.