UESP lists stagger values for each weapon type: http://www.uesp.net/wiki/Skyrim:Weapons

The highest stagger value is for warhammers, at 1.25; lowest is for swords at 0.75. (Daggers have a stagger value of 0, presumably because they never cause stagger.)

But to what do these numbers refer? The chance of causing a stagger, or the length of time the stagger lasts?

UESP also notes that stalhrim weapons have a higher stagger value by 0.1 than their non-stalhrim counterpoints: http://www.uesp.net/wiki/Dragonborn:Stalhrim

This means a stalhrim warhammer has a stagger value of 1.35.

You can see where I'm going with this. If a stalhrim warhammer is the staggeriest weapon in the game, how much more staggery is it in practice - and am I looking for increased frequency of stagger, or increased duration of stagger, compared to non-stalhrim warhammers?

Those numbers refer to the amount of time staggered; it appears to be measured in seconds, and (according to Creation Kit Wiki) is soft-capped at 1.0, which is the full animation.

Say you have a Stalhrim Warhammer. Against something that takes normal stagger, you get 1.0 (full animation) stagger. If a target only takes half stagger (eg, the heavy armour perks,) you'd get 0.675 (half of 1.35,) not 0.5 (half of 1.)

The chance to stagger is fixed by attack-method:
-Melee: 100% on power attacks (if the attack has a stagger magnitude, which daggers don't)
-Impact (destruction dual-casting): 100%
-Crossbow inherent: 50%
-Power Shot archery perk: 50%

Ah, thanks!

So the Stalhrim Warhammer's extra stagger value really seems to be a minor - or even nonexistent - benefit.

Do you know, offhand, if any in-game NPCs actually have the Tower of Strength perk? (I believe that's the only perk that reduces stagger.) If so, using a Stalhrim Warhammer could have *some* benefit (in terms of increased stagger). If not, may as well use any old warhammer.

***Just a side note, but I'm sure you've observed that in actual play, melee power-attack staggers don't always trigger when you'd expect. My guess is that this is just the result of an NPC's animation interfering.