which is the most important accounting function to an organisation: performance management or auditing and assurance?

1- Management accounting :

The purpose of management accounting in the organization is to support competitive decision making by collecting, processing, and communicating information that helps management plan, control, and evaluate business processes and company strategy. 

2- Internal auditing :

Internal auditing is an independent, objective assurance and consulting activity designed to add value and improve an organization's operations. It helps an organization accomplish its objectives by bringing a systematic, disciplined approach to evaluate and improve the effectivness of risk management, control and goverance processes .

Thank you

Performance management

in my opinion auditing and assurance.as it increases the performance management by itself.