It all depends on the types of monsters, not necessarily their armor levels.
For example, when imbues first came out, a guy did some pretty detailed damage tests of AR vs CS against tuskers. He found that AR was generally more useful (ie did more damage overall) on monkies starting at Rampager and going upward. That is, of course, on unvulned and unimperiled monsters.
In a more obvious and notorious difference, AR is always less effective than CS on Crystal Golems and Crystal Lords. Why? Because they have negative armor level, so the AR actually reduces the damage that a negative AL would normally allow you to do.
I find that while Virindi are pretty much equally vulnerable to fire and slash, my AR fire dirk can take Inquisitors down much faster than my CS slashing dirk. Of course I have to cast Imperil VII and Fire/Slash Vulnerability VII, but the Inquisitor's armor is still high enough that AR is better.
In Death Valley, my roommate always uses CS with his archer, but I think that's because he likes seeing the big numbers of the criticals coming often, rather than the elevated regular hits with AR. However, there are a few monsters where CS is significantly better, notably Drudges and Lugians. That's because it's pretty much assumed that you're going to have mage support, and those two classes of monsters go into negative AL with an Imperil VII, which translates into humongous damage from a CS weapon, and only just really good damage from an AR weapon.
But in most cases, AR works better than CS out in Death Valley because of the high AL of the monsters.
Also, AR is heads and shoulders better than CS when fighting monsters with shields, UNLESS you can lure the monster's shield enough to go negative. And luring shields is only worth the time on Death Valley Tumeroks and Undead. Regular tumeroks and undead go down quick enough with a regular AR weapon that luring is usually unneccesary.
So, being a low-strength dagger char, what do I carry around? CS slash/pierce, AR fire, and sometimes an AR frost, though I just got CS on a frosty, so I'll probably switch to that one. That does well enough on about 98% of the hunting I do.
