i am a software engineer, and i really love my job, so i pay all my passion on it. my suggestion is, choose with your interest.

A doctor eg a GP [ General practitioner] is on call a lot and works exhausting long hours & can always be sued for malpractice. An engineer[depending on his field of expertise] mainly works with machinery. Choose whether you like to work with people or machinery.

Both. It depends on what YOU like to do, in a different way these type of works help community.

be an entrepreneur

To a human, a doctor is better. To a machine, an engineer is better. It really depends on yourself who you want to work on...