Saying that 440C is excelent and other grades are not is wrong (or at least incomplete)! It is all about what you need the knife for. If you ever tried to cut bone by hammering the knife into the spine, you probably know 440C is brittle and will chip. In this case, for better impact resistence you need something less brittle, with a lower carbon content. And that is 440A or 440B.
Look at Noss's tests on knifetess.com and see how some 440C knives perform (for example the Smiss&Wesson) and look how the 440A knives perform (for example the Cheaper than Dirt Rough Use Knife) and you'll see that 440A is much more tough and strong. If your first priority is edge retention, than 440C is the best, otherwise 440A is the choice. 440B is an intermediar step between the two.
Look at Noss's tests on knifetess.com and see how some 440C knives perform (for example the Smiss&Wesson) and look how the 440A knives perform (for example the Cheaper than Dirt Rough Use Knife) and you'll see that 440A is much more tough and strong. If your first priority is edge retention, than 440C is the best, otherwise 440A is the choice. 440B is an intermediar step between the two.