Brass case is generally preferred, but steel is not the devil it's made out to be.
Steel cased will usually be cheaper, and depending on the gun it will run as good or better.
Case in point- I have a C308, which is the latest iteration of the Cetme from Century Arms. I know, cheap terrible gun made by angry beavers... but that gun has been fine, only a couple issues. I had 2 failures to extract, both with Armscor brass. The Cetme, like the HK and PTR, has a fluted chamber, and softer brass can flow into the flutes and get stuck. Steel has been 100% reliable, as has surplus Korean (PMC?) brass. This gun beats the daylights out of the cases with ejection, a lot of people say they can't reload them anyway. I don't reload, so I run what works in it.
Similarly, with my SKS and pistols in 9 Makarov caliber, I've shot 90% or greater steel, with no issue. I have shot some brass in the Maks but it doesn't seem to make a difference, so why pay more? I bought some of this earlier this year, the Tula 7.62 was $210 a case, the Silver Bear 9 Mak JHP was $190. I keep my CZ 82 loaded with 12 rds of the Silver Bear, with 2 spare mags. I don't know if it expands, but for that price I won't complain. It's plenty accurate at the range.
I picked up some entry level AR's recently (earlier this year, while I could still find some at/below the $500 point), picked up a case of IMI brass, then picked up some steel (2 cases of Tula, 1 case of Silver Bear). The IMI was 369, the Tula was $250 apiece, the Silver Bear was under $300. my AR's shoot these. Initially had trouble with Silver Bear with one, but a good thorough cleaning fixed that.
For point of reference-
Silver Bear .223 62 gr JHP, $280 for 1k, end of July.
Silver Bear 9x18 Makarov, $190 for 1k, end of June.
Tula 7.62x39, $210 for 1k, middle of July
Tula .223, $250 for 1k, middle of July
Tula 9x19 fmj, $167 for 1k, end of May.
Prices have surged since then, but the initial covid panic was underway by then (we didn't have the riot panics yet). Brass at that point was scarce and starting to climb.
It's not the best stuff, but it goes bang.