Have a warrior alt, thinking of leveling as prot.

[Taelas]

You'll not want the dagger. Daggers get less out of Attack Power than slower weapons do, as their speed is normalized at 1.7 for instant attacks while 1-handed swords, maces and axes are normalized at 2.4 (regardless of their actual speed). In other words, if you have a dagger and a sword with the exact same stats and you use them for Devastate, the sword will hit harder. Damage from attack power is calculated by dividing the AP with 14 and multiplying by the weapon's speed. For instant attacks, weapon speed is normalized.

Daggers can be okay choices for a tank, but not compared to weapons in their own itemlevel range.

That being said, tanking and soloing as Protection are somewhat different. Not by a great amount, as you're using the same abilities, but there's still a difference. While tanking, you want a fast weapon to maximize your Heroic Strikes, as that gives more damage than the difference in damage from Devastate would be with a slower weapon. While soloing, you won't have enough rage to do that, so you'll want a slow weapon to maximize Devastates.

Oh, and I'd choose the Venerable Mass of McGowan. It has less crit, but more AP and stamina, and you'll get dodge from the agility on it.