Rust is a big problem. If your set gets rusted, and it will be dangerous to use!
Depending on the type of steel, of course. Stainless steel is an answer to that, but not every manufacture is on the same page here. Rust still appears on our knives and scissors if left unattended for a few days. I noticed that kitchen knives from Europe, such as Zwilling Henckels or Wusthoff and other brands, get rusted more often than knives from Aisa, like Mac, Shun, or Nagomi, for example. Nothing but a personal observation.
Rust thrives if you keep your knives near the kitchen sink or other places with a high moisture level. It is a chemical reaction where water and oxygen get in close contact with iron in a knife, causes iron to oxidize. It doesn't happen fast but can be quite distractive.
Rust is manageable if timely removed with the hard side of a dish sponge. But if you are the one who loves having a ton of knives and uses one or two from the whole set, rust may appear unnoticed and cause quite a lot of damage. In this case, I would think about the necessity of the number of knives I have in the kitchen and act accordingly. I, personally, prefer to have no more than four to five knives in my set.
Currently, I have two chef knives where the one is a heavy-duty knife that can cut through bones or even a can of tuna if needed, and the other chef is pretty much for everything else. Among those two, I also have a Nakiri knife for vegetables. Two prep knives for boning and something small also have room on my table. It is a good set where each knife regularly gets used and has a good knife sharpening service. My choice is Japanese knives, they averagely lighter than knives from Germany, for example. Most of them keep a good balance between the handle and the thin blade.
But the other side is that they typically cost more than their European competitors.
Scratches matter from the esthetical point of view rather than on practice. As long as you are not cutting through a metal sponge or something that can damage the blade, not likely your set will ever get scratches on it. Deep scratches are hard to get removed, to the point where it is unreasonable to remove them at all. As long as you keep your knives away from unskilled hands and take care of your set, it will serve you for a long time.
I find it attractive when a knife has a little bit of shine. Recently I bought a polishing wheel and attached it to one of the grinders I have. I love the result that I get from it! A polishing compound on the wheel helps to give the knives that light shine.
After I started including rust removal and polishing in my knife sharpening, my customers noticed a huge before/after difference. Their cooking experience got better now they look forward to using their knives again. I cannot be happier to see the positive feedback from a customer a few weeks later after visiting me. It means I move in the right direction.
Keep your knives dry and clean, it is not hard to do.
We specifically work with kitchen knives (serrated or straight blades) and fabric/kitchen shears. We DO NOT sharpen swords, ceramic knives, curvy knives (karambit type), all blades without a handle, straight razors, garden tools.