As an engineer, I absolutely love the science behind heat treating steel. Getting to visit with guys like Devin Thomas about it is fascinating and you soon realize you don't know nearly as much as you thought.
This is probably getting way off topic, but I'm bored this a.m.
There are some steels that are extremely tough, but horribly inadequate in the strength department.
Here's a really interesting chart:
Toughness in steel is it's ability to resist chipping or breaking....simple definition.
Wear resistance in steel is pretty self explanatory....how well it resists wear. This is the attribute that knife makers hate. High wear resistant steels are a biotch to grind.
The chart doesn't show strength. Strength is a steels ability to resist deformation....simple definition.
Strength and toughness are usually polar opposites.....raise the strength, lower the toughness. Makes sense, right? Raise the hardness of the steel, the more likely it is to chip (lower toughness).
As BDL stated, finding a great balance is the goal.
However, and this is especially true in kitchen knives, we have other factors to consider. We want a steel that is both tough, wear resistant, and strong...but also able to take a very keen edge.