If budget is not an issue. I would go with the EXT or EX machines. EX has a little more power, both weld about the same. EXT has a couple hidden setting that are nice. EX you see all the knobs are a glance, EXT is easy as well, as you normally will not move settings once dialed in.
Hope that did not confuse you. If nothing else, you can not go wrong with the flag ship 250EX. If you want simpler, 210EXT once you set the settings, basically, pick amps and AC/DC and go. I have and use both.