Shima
Omono
Not necessarily. Really a lot come into play for performance of a steel and big determining factor is heat treatment. Much more than just the composition of the steel. A good reputable producer or seller should have a good heat treat sourced to get the most out of the steel they use.
It's been said already but carbon steel will hold and edge better than ss. This is not universally true but for an SS and CS at the same price point the carbon steel will perform better. The reason is because of the chromium content in SS. While it gives the steel corrosion resistance it also makes the steel more wear resistant. This makes the steel harder to machine or work thus increasing production cost. So in order to offer an SS tool at a similar price point to that of a CS tool they will use a cheaper grade of SS. What American Bonsai and many others use is 440c steel. A cheap stainless but works well enough.
There are very high performing stainless steels out there but the high wear resistance make them impractical and too costly to use in something like bonsai tools. Another thing to consider is tool maintenance. Many high performing stainless steels are alloyed with chromium and vanadium which create hard carbides in addition to being heat treated to a high rockwell hardness (HRC). Steels like that require diamond and ceramic abrasives to cut and sharpen the steel. Depending on application you need to find a balance between performance and ease of maintenance. I own a set of expensive waterstones from my knife enthusiast days as well as diamond plates so this does not bother me. But average person will not own expensive sharpening equipment so it'd be difficult to sell expensive SS tools with high performance.
Many carbon steels on the other hand have a fine grain that produces a keener edge and is easier to sharpen. For most practical purposes no one really needs the performance of high end SS steels.
If you do not live in an overly humid area and you're responsible enough to occasionally clean/maintain your tools buy carbon steel. They will perform much better.
The more premium Japanese bonsai tool makers will use "blue" or "white" steel. The better grades have a higher carbon content which improve wear resistance and edge holding.
Finally...some metallurgy. It's not just SS or black.
And here's a bit of back story on Masakuni and a certain scissor favored by Peter Warren who knows a thing or two. http://saruyama-bonsai.blogspot.com/2011/05/tool-of-champions.html
And I DO live in an overly humid area and couldn't do without Corrosion X. Sold at fishing shops. None of my black tools have rust. I wipe it on now and then, at least the cutting edge, leave it on and wipe it off the next day. https://www.amazon.com/product-reviews/B0009GYRWW
