Both are important but if you're trying to be practical, empathy is where you want to be aiming.

Empathy is the ability to put yourself in other people’s shoes. You view the world through their eyes and feel what they are feeling. It is important in business, marketing and everyday relationships as well as a thought exercise for yourself. 

Sympathy also describes the situation where you relate to someone and understand their feelings. However, the crucial difference when you when you experience sympathy is that you become so wrapped up in the feelings that they transfer to you as well. This robs you of the ability to maintain a critical distance and help in a situation.

In summary, sympathy describes feeling emotions like pity and compassion, whereas empathy is an exercise in putting yourself in the situation of someone else.

Why is empathy important in marketing?

From a marketing point of view, empathy is a valuable skill to develop as it often provides insights into how your product or service is viewed which can often be missed in by the in-house team.