What is the main difference between the Finance, Sales and HR specializations in management? Which is best for engineers?

The streams that you are talking about are different branches of management. The answer to your question lies in the stream of your interest.

Sales come under marketing and finance,HR and sales all are totally different. Finance is dealing with money, investment,budgeting. HR is handling and managing the human population in an organisation and Marketing deals with product/services positioning, customer satisfaction, brand, advertisement e