Should I attack Clay Cox in Vampyr? Vampyr Guide and Walkthrough

When playing Chapter One of Vampyr, you will soon encounter Clay Coxa - whom you will hypnotize. Doing the Take me to the hospital mission, Jonathan will grab him, and you will have to find a secluded place. You'll have a choice - suck his blood, and kill Clay Cox, or release him.

• If you release him, you will meet the man in a later game. He will be a regular resident of Pembroke Hospital, will offer you one investigation to do, etc. You will also be able to find tips that will tell you more about Clay's history.
• If you drink his blood, you'll get a healthy amount of XP, and the man will die. The health of the district will decrease, and you won't do Cox's investigation, obviously.
• Both choices yield different achievements. You cannot load game in Vampyr, so you can't obtain both achievements in one play through.
• You can drink his blood later. You shouldn't kill Clay right away - if you have to, you should complete his missions first, learn a bit about him, and kill him then.
• If you want to complete the game without killing, you obviously have to spare him.