Depends on your style of play. If I grouped and had a priest with me most of the time i might go retribution of increased defensive and dps capabilities.
Otherwise, the advantages to the Holy line are huge, especially when soloing. Most importantly are the abilities which give you a 70% chance to not gain any more casting time when struck, to be able to critical heal when you choose, once every 2 minutes, and to regain the full mana cost of every critical heal.
So basically you get a mana-free critical heal once every 2 minutes. This is huge if you like to solo, especially if you like to solo in difficult areas. Also not gaining casting time when struck is pretty huge if you are a soloer. Plus the end bonus ability is nice, a 200 nuke that gets upgraded as you level, this is awesome for taunt. A stun and a nuke at the beginning of a fight allows the dps classes to just wail on mobs while you hold aggro easily.
The only thing i really miss by going holy line is +5% to crit, and the +5% damage on 1 or 2 handers, your choice, and Blessing of Kings is kinda nice in a multipally group.