The running amperage load on the MM 211 is 25A @ 230V and when you do the math (A x V = W) it comes to 5750 watts. The problem is it does not show the starting amperage load and typically MIG welders require a steady sine wave along with high starting.
I've heard a good professional 7500 watt generator could handle the load as long as you keep the amp output low because when you jump to 175A output or higher the unit will struggle and your welder will not keep a constant arch.
The larger generators have higher output capacity but you are limited to the 50A outlet so your going to max out at 12,500 watts on them and might still have problems.
If you keep the welds to 1/8th and under or short welds you would be ok but that never happens.