>Halt v. Stun Foe
It has been my (limited) experience that most paladins weight their stats toward SvS not WvW, to which it comes as no surprise that most prefer Stun Foe. However, immobile is a more penalizing state than stunned, off balance, or prone. So all things equal (as in assume you can be equally successful with Half or Stun Foe) you're better off immobilizing your target for PvP. For PvE immobile gives an exp penalty (I think) whereas stun/prone/off balance does not, therefor Stun Foe is a better choice.
I think all that's right at least.
~Hunter Hanryu
http://drplat.com/CombatEquipmentCompendium.xls
Tolle says, "Yup yup, 'bout time. What the heck took you so long?"