Nickel and stainless are different metals that look very similar. They both come in matte (satin) finishes. Some all-nickel (vs nickel "finish") faucets (mine are Dornbracht and Rohl) will tarnish slightly over time and require maintenance similar to polishing silver. I use Flitz for that (though it isn't needed frequently).

I'd find out if a nickel faucet have protective coating, which some nickel-finish faucets do. Those might simply need wiping down with a soft cloth, just like stainless.

Okay, thanks. True stainless is steel mixed with a little nickel, isn't it?

I just hope I can get these faucets to match. My prep faucet says nothing about any coating, and it seems to be just bare metal.

See the link on the stainless composition.

IME if you want a perfect match then stick with the same brand. But a blend can be fine, too. It depends on each piece.

The thing about the finishes is that the highest end faucets are all metal and more popular priced faucets may be nickel coating on another material. The weight of the faucet will let you know, generally, how much metal it has. The heavier the better.

But the process for creating the finishes is quite good and its rare to hear of a faucet finish wearing badly.

If there isn't info on the finish then I wouldn't use the polish, just a microfiber cloth with whatever cleaner the manufacturer recommends for their products. My satin nickel faucets clean up really well with a microfiber cloth. No babying required.

Here is a link that might be useful: composition of stainless steel