Headshot from VoC is Almost 900; Vex after getting a couple kills for Crowd a control is around 650 a headshot. VoC has a max mag of 27x880=23,760 Vex has a max mag of 35x650=22,750. The vex does have an increased fire rate, but the amount ammo you burn through is ridiculous. The VoC has a WAY higher ammo reserve and allows you to equip a different exotic such as Ice Breaker or Ghorn. I very much wish to see the Vex destroying enemies in PvE, but right now it's not as viable as the VoC is in the harder activities like the nightfall. I'm not saying the VoC is the best primary in the game, just (as they are now) that it is better than the Vex.