TL;DR – For PvE DPS: Sharpened > Precise > NirnhonedPrecise can be better for organised groups running most armour debuffs in the game
When evaluating between these three item traits it is imperative to recall the average damage formula

where

The skill coefficient,
a, depends on the skill in question and an excellent list of skill coefficients can be found at
http://esoitem.uesp.net/viewSkills.php.
b is around 10.5 for most abilities. Attacker Bonus refers to certain Champion Points like Elemental Expert, Mighty or Thaumathurge and includes certain skills and passives such as Major or Minor Berserk. For simplicity, we can just set this to one and ignore it for the large part.

Armour debuffs include Major/Minor Breach, 5 piece bonus of Roar of Alkosh and the Crushing Enchantment. An example of percentage penetration is Penetrating Magic (Destruction Staff). Flat Penetration includes the base penetration of 100, Concentration and Spell Erosion/Piercing.
In order to compare the three traits, we can convert both the additional flat penetration offered by Sharpened and the extra critical chance into Spell/Weapon Damage. Finally we can convert the Spell/Weapon damage equivalence to an increase in an arbitrary ability tooltip.

I’ll use a generic magicka build as an example, I’ll assume a Magicka pool of 40k and Spell Damage of 3k which is reasonably typical for endgame builds. Only legendary trait values are considered.
Nirnhoned
It increases the tooltip value of a weapon by 11% which in turn increases Spell/Weapon damage by 11% before any buffs. For a staff, this corresponds to a base increase in spell damage of 146 Spell Damage and for dual wielding swords it corresponds to 175 Spell Damage. Typically this base spell damage is buffed by 25% by Major and Minor Sorcery. So you would expect 183 Spell Damage for a staff and 219 Spell Damage for dual wielding swords. Thus if we’re dual wielding swords, Nirnhoned leads to an increase ability tooltip of roughly 3.2%.
Precise
The 7% increased weapon and spell critical can be converted to an equivalent spell damage with the following equation

A reasonably common spell critical for endgame builds is around 60% and a critical modifier between 0.6-0.7 is typical for most magicka builds. This assumes around 30 points in Elfborn which is a fairly common recommendation from my Champion Point optimisation spreadsheet (
https://docs.google.com/spreadsheets/d/1Zp9v1Vp4Z7X6zfDfcxTwyAnejv-tEC5LujbXYBiVMDk/edit?usp=sharing) thus the spell damage equivalence for Precise is about

This translates to an increase in average ability tooltip by 3.5%. Note that we can reach this answer quicker by noting that
Sharpened
In a similar fashion to the previous section, the increased physical and spell penetration of Sharpened can be converted to an equivalent spell damage or more directly into an increase in ability tooltip

where Mitigation has been separated into a Sharpened component and everything else. The key concern here is that the Resistance of a target cannot go below zero. Let us consider a typical 4 person dungeon, bosses have around 18k resistance and trash have anywhere from 10 to 18k resistance (
http://tamrielfoundry.com/topic/2-1-boss-resistance/). The main source of armour debuff is Major Breach (5280) and Flat Penetration for Magicka Characters is at least 4984 (100 base + 4884 Concentration). Flat Penetration is typically higher by around 1-2k depending on the number of points assigned into Spell Erosion. This means the average boss will have about 6.5k resistance and 100% of the Sharpened bonus is used meaning that it increase ability tooltip by

Unfortunately, Sharpened is useless on any mob with less than about 12k resistance as its resistance is already reduced to zero from other sources. So at first glance, the optimal trait seems to be Sharpened for bosses and Precise for trash, similar to the meta on Live.
But there may be another way around this, given that we are reaching unmitigated damage it is reasonable to remove all points from Spell Erosion and apply it all into Elfborn instead. Then a more interesting question would be how much resistance does Sharpened need to remove for it to be equivalent to Precise. Precise provides 3.5% increase in ability tooltip, this value can be achieved if Sharpened removes at least 1750 resistance. My optimal champion point spreadsheet tends to suggest around 30 points in Elfborn which corresponds to this value. Thus it is possible to simply use Sharpened for most trash and all bosses and put 66 points in Elfborn (67 points in Elfborn works the same as 66 points so spent the last point in something else like Staff Expert. In this way Sharpened is acting at worst equivalent to Precise but you get additional points in Elfborn thus increasing your average damage or it significantly outperforms Precise on bosses.
Although I've only discussed magicka builds primarily, this conclusion of using Sharpened in most situations holds true for stamina builds as well. Stamina builds do not have a Flat Penetration skill but this is compensated by several armour debuff methods.