OK, this brass vs. steel cased ammo test by Luckygunner is for AR's shooting 556 ammo, not pistol ammo.
However, it's the most exhaustive test I've seen yet. 4 new carbines, each one shot fast with 10,000 rounds of brass or steel cased ammo. Macro pictures, measurements of pressure, slow motion capture video of cyclic rate. The most helpful part to me was the in depth picture of extractor wear (zoom way in if you have a decent computer / internet connection), and the cost effectiveness line graph at the bottom.
https://www.luckygunner.com/labs/brass-vs-steel-cased-ammo/#erosion .
Long story short, for AR's, you maintain better accuracy, cyclic rate through less fouling, maintain bore / throat integrity by shooting brass cased AR ammo beyond 10,000 rounds under rapid fire with a chrome lined barrel. Steel cased barrels were "shot out" at 6,000 rounds. But if you factor in cost, you could replace the barrel twice within those 10,000 rounds and still save $1,000 by the time you bought / shot 10,000 rounds.
What would be different for semi auto pistols? Well, in the test all rifles were shot so fast that they were too hot to hold - probably to accelerate wear to make the differences more significant. What if the rifles were actually shot at a more realistic pace? Like maybe a string of a mag or 2 as in a stage in a competition or doing drills? I'd imagine the barrel would not reach nor sustain the temperatures met during the test. And pistol ammo doesn't reach the same chamber pressures / temperature as rifle either, 9mm is about half max pressure of 556. So that would make for even less wear.
If we apply the same conclusions: If you want cleaner cycling, more theoretical accuracy, less theoretical wear on extractors or barrels, shoot brass. But if you recognize that barrels and extractors or bushings (where applicable) are replaceable - heck even complete slides are available, then shoot away, you may end up saving in the long run depending on cost of replacement parts. And that's if the lower pressured steel cased pistol rounds (compared to rifle) could even erode anything with flame cutting.
These days an aftermarket Glock barrel can be had for ~$55 shipped. Crazy.
The accuracy bit is more significant on a rifle, whereas on pistol the human is usually the limiting factor unless you are shooting bullseye with a tricked out pistol.
On a nice old revolver though, I wouldn't be able to replace a barrel as easily so I'd go brass. And I reload.