Attention quiet introvert: Solving problems is your job as an engineer. All of those problems are problems that people have. Frequently the people can't even express what or why it is a problem. They know its a problem, and its probably your fault. The number one reason why engineering projects fail is poor definition of the problem. The wrong problem or no problem gets solved. Communication along with patience and perserverance is the antidote to poor problem definition. You don't have to like everyone. You just have to listen to them, communicate with them, and do your best to learn what their real problem is, not what they think it might be. The real answer is it doesn't matter what branch you choose based on quiet and introverted. You will have to work with people regardless of your branch. What those people will be like is difficult to predict. In my career, I have worked with lots of different people in lots of different industries. It has been critical for me to listen and learn in every situation I am in, first project in a new company, or 500th project in an old company. I do not have to be best friends, or even good friends with the people I work with. I just have to work with them. Make sure you have interests outside of work.