So I have confirmed that it is indeed steel by doing the magnet test
Good cogs are made of tool-level hard steel. Plating will rub off on the teeth if they work. You have to apply protection no matter whether you start plated or not. The only practical reason for going with plating is that it is likely to correlate with the overall amount of effort going into the manufacturing.
The reason I made the thread is to figure out if this cassette which has extra holes carved out for weight reduction is as durable as my other cassette which doesn't have weight reduction in design and has started rusting because it was left outside for a while. I wont to figure out which ones I should use for my main bike.
I had thought the silver one is worse because it may not be steel, but turns out it is steel. The other set has already started rusting, and rust can cause friction and furthering wear.
