Steel does wear the extractor faster than brass.
I keep wondering where this idea comes from. The only real difference between steel and brass cases in use is that the steel tends to spring back faster which means as the pressure drops in the bore the steel relaxes its grip on the chamber sooner. Less grip means less energy required to pull the case from the chamber. Since most firearms don't pull the case from the chamber, it pushes the bolt back through residual pressure, that isn't even an issue. Look at the number of small handguns and rifles with no extractors....Beretta 950s come immediately to mind. The case pushes the slide back, the extractor doesn't pull the case out. This is true of your 1911 and most other semi auto firearms too.
Every steel case I've seen in commercial or military use has a coating which is softer than brass by far. Laquer was popular, copper or other metallic plating, polymer coatings etc. Every one of those is softer than brass and far softer than the steel of the firearm. For that reason even if there was a wear issue with cartridge cases rubbing somewhere on the firearm (there really isn't) the steel cases would cause less wear than brass.
Since the steel is not actually bearing on the extractor and in reality the soft steel of the cartridge case is substantially softer than the hardened extractor there is no more wear from steel than there is with brass. There is no more load on the extractor with steel because it comes free from the chamber quicker than brass and has less drag in the chamber. Because of that one thing I'd be more inclined to believe that brass is harder on extractors than steel. If the effort required to run with steel was really that much higher I'd expect to see soft crappy brass cases with bent rims a lot more often. So in reality, if the brass cases don't have bent rims from the extractor, why would the steel cases make the extractors break sooner? Why would steel wear the extractor more?
As a simple example from my own experience, a tale of the steel vs brass.
I had a post sample thompson 1928 SMG. We ran about 7000 rds of steel cased wolf ammo through the gun doing demos and machinegun shoots. I broke an extractor. It took us about 4 mags to finally figure out the extractor was broken because the gun ran fine with occasional cases being dropped back into the feedway. Maybe once or twice per 30rd mag. So I replaced the extractor. We ran a few thousand rounds of steel cased wolf through the gun with no issues. I got to a shoot somewhere and we ran out of ammo but a customer wanted to shoot the gun. He had a couple boxes of S&B brass cased 45 auto. We let him load up a couple mags and run the gun. After the first mag we had some odd issues with empties dropping back into the feedway and guess what? Broken extractor. So did the brass cased ammo break the extractor? All that steel ran fine but 100rds of brass killed it? In reality thompson extractors seem to last about 5000 rds or so and it doesn't matter whether its steel or brass cases. Not a measureable difference in anything we could detect. Rate of fire is the same, reliability is the same, wear is the same.
No real difference. So I say, shoot what you want, reload what you want, don't let guys scare you with tales of doom and gloom when most of them haven't even tried what you're asking about, they just have internet myth.
Just my 2 cents corrected for inflation
Frank