Almost all of our welders (TIG, MIG, Stick) as well as one of our plasma cutters are made for 230V. We run them at 208 with no problems. More and more you'll find today inverter machines that will accept anything from 208v 1Ø to 480v 3Ø without changing any of the taps. If you have taps for 200v, use those. Lastly, if your machines are CC/CV sources then it really shouldn't matter except on the top end of the machine since they'll compensate for the reduced input by raising their output accordingly.