You should learn at least a little of each one to do the other, but you can specialize in one. Data science is about building and assessing machine learning models. It uses more mathematics and advanced statistics. Data engineering is about cleaning and storing the data, getting the data to flow through those models, and making the results available. It can use advanced statistics, but uses more programming and network engineering. Salaries and prestige tend to be slightly higher for data scientists compared with data engineers, but either one could be the key to the success of a company. A small company might need one person to do both. An advanced degree is more valuable for a data scientist than a data engineer.
