Discuss the distinct roles that Equity Capital Markets (ECM) and Debt Capital Markets (DCM) play in corporate financing. What are the key characteristics, advantages, and disadvantages of each?

你认为股权资本市场（ECM）和债务资本市场（DCM）在公司融资中扮演着怎样不同的角色？请简单阐述它们各自的主要特点、主要优势和劣势。