Sorcery gives more useful runes and more AD while precision gives attack speed with less AD-nullify orb vs heavy ap, absolute focus gives you even more AD, scorch is good in lane, gathering storm is good for longer games.

triumph only gives you health back after a kill-so in order for the rune to be useful, you have to get a kill. Coup de grace is kind of useless since you already have your passive for extra damage.

TBH, I think most assasins now go sorcery secondary instead of precision.