In MMOs, I quite like a full healing, such is the case with Ragnarok Online because I often don't have time to go to the menu and heal straight away afterwards. However, I don't mind too much otherwise. I'm generally happy for my HP to increase in line with the increase in total HP, as I dislike having all of my HP but 3 or 4 because I know it's not a big difference, but I also know that there have been times when I've survived a battle by 3 or 4 HP and worry that perhaps it'll leave me at a disadvantage.