More TIG questions

I haven't used any of the new machines to be able to tell you which is best. What I did when something new came out was to compare the arc stability with a Lincoln Pipeliner as there's nothing that beat the Pipeliner for arc stability.
If it was me I would make them hook up one on each machine and try it as if there's a small difference you'll see right away.

Setup is about the same between any Tig machine. If welding below 150amps then dry torch work well and if above 150amps then wet torch keeps the torch cool while welding but is about $1200 extra cost.

A scratch start Tig torch is the cheapest as it can be added to any DC machine. Amps are adjusted at the machine, the flow meter turns the cover gas on and off, and the Tig torch lead is clamped in the stinger lead. You do not have to have a special machine for Tig welding. I say DC because it has a better arc than AC but AC can also be used. This was a common method for Tig welding during the 70's and 80's. Amp foot and hand contols are nice but not needed. Gas valves are nice but not needed.

T_Bone