Unlike Paladins where 30 Vit is really the only serious option, Warriors get a lot more out of Strength than their shield-using cousins.

For paladins the choice is around 7% increased damage/threat vs 10% max HP (roughly, in average 50 gear). For Warriors, it will be the same choice, but the Warriors get a lot more options that scale damage output into self healing.

Personally I'm going 15 Str 15 Vit on my Warrior, but I really feel that there's no bad choice for Warriors here. It's truly a personal choice as both are effective.