So I am not sure what is actually the best, but what I can say is far too many times have I seen my HP at 100 or 300 in coil and I am currently using 30/30 VIT (Have not run coil since pickiing up my af2 chest). What this tells me is on those few attempts, my WAR is dead and boss attempt likely wiped if I had switched to STR.

Have I done a kill on coil turns where my health never dropped below ~500? Yes, but more often then not it does, and until I can say that most of the time it will not happen, I will stick to my VIT which helps in coil. I'd rather pick up some STR ring/neck/ear and drop my VIT ones for most content (basically all but coil) until I have the needed gear to switch my stats for everywhere.