I couldn't google an answer to my question and I decided to do a little research of my own. The question is at what point is it better to have life% increase over vitality increase. Example: At 16K life is it better to have +5% Life or +23 Vitality?
The answer is vitality by a small amount.
Here's what I did I removed all my armor, recorded my HP and Vitality, then put on my armor and recorded the result once more. I put it in excel and made a little chart.
X axis: HP
Y axis: Vitality
Each point has the exact number next to it (hp, vitality)
This is from my level 60 monk, I don't know if your numbers will be different.
Now math isn't my strong point so correct me if I'm wrong I figured the ratio for viatality to HP is 5:179
So with that you can figure out what's the best piece of equipment to use to buff your HP. From what I've seen at the auction house its almost always better to have extra vitality where high level equipment can get you +150 to +175 and life% at best gives you +12%.