I would purchase and own a stainless gun with no fears, since I know that modern manufacturers have done what they needed to do, and with good lube hygiene I just wouldn't be too worried about it.
I've built two 1911s so far from the ground up, and the first one was stainless. There's a reason the second one was not stainless. I will almost certainly never attempt another stainless 1911 on a scratch build.
Short version: I didn't understand what galling was about, and while fitting my slide to my frame I decided to try the "tap on, tap off" method using some fine grit on the rails. Tapping a stainless slide onto a stainless frame will result in almost instantaneous galling. The parts literally weld themselves together at the microscopic level where asperities in the surface contact each other at high pressure. I had to beat the slide back off with a rubber mallet and a shocking level of violence. So I tried to be more careful, and was for a while, then I galled it again. So, I gave up tapping on/tapping off and used at most some hand pressure to work the grit where it got tight. Guess what? If you push a tight slide onto a frame a little too hard by hand it can or even will gall. Who knew? Not me, that's who.
So yeah, I experienced galling something like 4 or 5 times while fitting my SS slide/frame together, and the frame rails still show faint evidence of the little trails impressed into the surface where little microscopic chunks of stainless steel had ripped out of the frame rail onto the slide rails and then been drug across the surface of the frame rails as I beat the slide back off with the rubber mallet. It's embarassing, and I hope none of you ever see this in person.
So, I've seen what galling is and the destruction it can cause first hand. But guess what? I experienced said galling because I was ignorant of galling and what caused it and how to avoid it, not because it is inevitable. I'm willing to give manufacturers the benefit of the doubt that they are not ignorant about successfully machining and fitting guns made from stainless steel, and that they do it right and it's just not an issue. I mean, there are zillions of gun companies making zillions of stainless guns, and there aren't zillions of stories of these guns locking up due to galling.
So yeah, I'd buy a properly made stainless gun, by which I mean I'd buy a SS gun from a company with a good track record of successfully making SS guns.
What I will not do, however, is attempt to build another stainless gun by hand, as I've done with my two 1911 projects so far. I got 99 problems, but galling on a new stainless steel gun project ain't one.
