Both of those machines are DC only, so no aluminum Tig unless you were to go old school and use helium as a shielding gas and do true Heliarc on DC.
Stainless Tig is done on DC, as is steel, at a bare minimum you need a dc stick welder (or an a/c welder with rectifier setup) to do scratch start Tig.
Scratch start is “old school,” but still used in the field all the time today, very capable, and simple. The Ford Fairlane I did the coil over install on was all scratch start Tig, besides a couple spots did flux core.
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Done with scratch start Tig with that circa 1978 TriStar welder
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Take a look at primeweld machines if you haven’t. I think for your needs I’d look at a dedicated MIG machine over a multi process. Also to consider a transformer vs inverter machine. The new inverter technology is pretty amazing and clever with what they manage to pull off, but some times you just can’t beat a pure mass of copper that is a transformer machine.
There’s a lot of options these days, and a lot of very competitive and good machines too.