Both options work well, but washing in the sink allows for more controlled water temperature and pressure. Some find the shower convenient for a thorough cleanse, but avoid hot water to prevent drying out the skin.
When showering try to keep shampoo and conditioners away from the face, it is a little bit difficult to completely avoid this but they can contain harsh ingredients and fragrance that can irritate the skin.
If you do notice irritation on the face (usually around and under the ears) after a shower this might be the reason why. It's probably worth considering a shampoo thats designed for sensitive skin to help prevent further irritation.
