What would you tell a loved one to train in for self defence; Shotokan Karate or Wing Chun?

If you Absolutely had to choose between the two I would lean more towards Shotokan Karate. They tend to have more real life applicable techniques and not fancy theoretical movies. The blocking system is very sound and the strikes powerful as opposed to wing chun which relys on multiple "weaker" punches/kicks to overwhelm opponents. If there were other options available though I would explore those. Gracie Jujitsu is very powerful and techniques can be learned in one day that can be immediately used in real life. Also the sparring which is called "rolling" is pretty safe and technique can be applied at close to full power and you know if you are doing it properly because if not it will not work. Some martial arts tend to give people a false sense of security when they haven't even ever really been tested.