Basically what happens in heat treat, the chromium carbides grow so large in those "lesser steels"
that the carbides will actually be larger than the grit you are currently sharpening with. A ot of the time there will be chromiums carbides in excess of 60 microns in cheap steel, not that ALL of the carbides are that size, but the average still tends to be much bigger than better steel. The result is what we call "carbide fallout" where the big chunky carbides actually fall out of the edge and cause it to loose that "off-the-stones" feeling very fast, but then will hold a semi-refined edge for a long time after. This is the case with most cheaper stainlesses and some of the 1st generation powdered metals, but the difference is that the cheaper stainless tends to not even hold the semi-refined edge for very long either.
So, the smaller the carbides, generally the tougher the steel, it will take a higher refinement and hold it longer, generally speaking, and should come back with stropping easier. An exception to "fine carbide" to "edge holding" argument, there's another sweet-spot IMO. Instead of having the smallest carbides, you can have a sweet-spot of nice sized carbides and better alloys. SKD11 tool steel might not have the finest carbides in the world, but it still takes a good refinement, and holds very well because the Chromium content is still below 13% (keeping in mind this is NOT a powdered metal). I love tool steels because they tend to have decent sized carbides, medium chromium content, but other alloys to make them awesome.
Don't get me wrong, I'm not knocking chromium, for without it we wouldn't have stainless, and it can help make a knife harder to take a steeper edge.. given the right circumstances.
And I see Adam beat me to the punch. Get a life!!!