Weapon Damage Types, and You
One of the things that greatly complicates matters on natural selection is the issue of armor and damage types. There are (for all intents) 4 main damage types on the mud - Slashing, Piercing, Bashing, and Exotic. What's key is that each type of damage has an armor amount associated with it; the exact amount varies from armor peice to armor peice (although spells add thier AC evenly). Since this is the case, it's possible to maximise damage to your opponent by using the type of weapon it's most vunerable to.
With players, the answer is always and forever Exotic. Exotic damage types include Divine, and shocking/acid/fire (it's key that these be the damage types - not the flags. The key way to tell is if your weapon does a:
Your sword Peirces the Knight!
Your flaming bite Scorches the knight!
then it's a flag, and not the damage type (flaming in this case.) If you've got the time, compare a jagged Tanar'ri to a shotgun - you'll see the diffrence quick.
The most common exotic damage type is Divine - sevreral weapons of several levels have it, including a level 60 dagger (33-sharp). If your into pk, i'd suggest picking one of these up.
Mobs vary in thier Ac, much like players. Though at current there's no way to accurately gauge a mobs AC as a player, it's assumed from some research that there are certain "standard" amounts of Ac, in the various catagories. Presumably it follows the same pattern as with players - being vunerable to exotic, and less so to other damage types. An interesting note is that some mobs who are immune to a given damage type (say, slashing, bashing, and piercing), are usually vunerable to exotic. A case in point is the master of disipline.
So, what's the "final verdict", you ask? That Exotic damage types are superior to non-exotic, in most situations. In some they won't matter - the mob will be strong against a given type, or your weapon will be inferior - but in the majority of the time, exotic damage types (particuarly divine) is better. So, i highly recommend you locate some weapons with differing damage types - especially if your into PK or other "time intensive" killing practices, where every second needs to be full of as much damage as possible.