Diablo – Smoke Screen vs Reflects Damage

Unlike in Diablo II, on-hit elemental damage is simply that - bonus damage, with the sole exception of cold damage (which has a small snare). Frost damage does a little less damage comparatively because of this.

While there was originally a more complex critical hit system (as documented below), that functionality did not make it to the final game.

Critical hits just add damage.

Historical Answer:

More interestingly, in the Diablo III Beta, each type of damage has a different effect on a critical.

• Physical: Double Damage

• Arcane: Silences targets for 4 seconds (prevents abilities)

• Cold: Freezes targets for 2 seconds (Duration can be affected by talents, etc.)

• Fire: Sets them on fire, fire DoT (tick rate scales off weapon speed)

• Lightning: Stuns targets for 2 seconds (Duration can be affected by talents, etc.)

Poison and Holy presumably have effects on a critical hit also, but I haven't been able to find info on them.

Skills that state "% weapon damage" will deal the elemental damage from a weapon. Skills that state "% weapon damage as (element)" will not. So the weapon's fire damage would come through with Spectral Blade, but not with Magic Missile or Ray of Frost.

If the skill deals fire damage, either "naturally" or from a weapon effect, it should activate Conflagration.

Some sources here, here, here.