Berserker. Precision isn't nearly as good without high crit damage.
Toughness alone is... bleh. If you're really going for a tanky build you need some toughness, vit, and healing. You need traits that heal you when you use shouts and weapon swap. Toughness alone won't do jack.
Knight is really, really good, just because it gives you a good balance between staying alive and damage. Its also a viable set for both going pure damage (maximum damage will come from melee, and having some toughness helps with that), as well as going support/control.
Once you can afford several sets, then the story's different, but if you can only get one, I'd pick knight over anything else.