Vests are a little different to helmets in terms of usefulness, but as always an undamaged level three will always be better than a level two. In the late game, if you plan to take a lot of fights then better durability is more important than high level. So a full health level two is better than a quarter health level three, as it will last longer. If it’s down to the last few people, though, then the damaged level three should be the better option, as blocking more damage from one shot could be the difference between a win and a loss.