I'm a MNK lurking here in your forumz for God knows why, so I don't know what I'm talking about, but I'd stack STR because:
  • VIT only increases HP
  • 8% more HP in the end game, while nice, feels relatively minor (especially as you get better gear and more HP this % will only decrease), whereas...
Strength plays into a WAR's mitigation and usefulness in several ways!
  • STR determines the damage mitigated when you parry. This becomes meaningful with Foresight.
  • STR determines your self heal, which is WAR's version of mitigation.
  • STR makes you hit harder, contributing to your enmity and your contribution to DPS races.
I'd also like to add that however you distributed your points via STR/VIT, you can always compensate with gear and materia.