Kda ratio is better as it eliminates the issue of score. I find the idea of awarding points on kill to whoever pulled the trigger last more irritating than anything. This method allows for the game to flow smoother and allows players to still get a reward when someone drops in and pops off a single round to pull the kill. (Assists are a good thing people.) There are other ways they could have done it, say based on overall dmg dealt but this is a simpler more streamlined idea. There are many more problem than scoring.