Use Google and look for comments by Ernie. He teaches welding at a
community college. The Lincoln welders are great, and I think they
include more advanced controls as standard than Miller. The water
cooled torch becomes important at higher currents. The 185 will
probably be as much as you need for stainless. Stainless does not
conduct heat as well as regular steel so less current is needed.
Aluminum is where the extra current is needed.

If I were you, I would also look at inverter welders. They are smaller
and lighter. I forget which one Ernie says is the best buy. Most
inverter welders do not provide AC, and are therefore not especially
good for Aluminum. But one of them does ( not Miller or Lincoln ).

Dan