The correct answer is C: Improving the top-down communication and coordination in the company. The establishment of an Enterprise Risk Management (ERM) framework is a strategic decision that aims to integrate risk management practices across an organization. By doing so, it allows for a more holistic approach to risk, where the interdependencies among various risks can be better understood and managed. This integration is facilitated by appointing a Chief Risk Officer (CRO) and creating a centralized, integrated risk management team. Such a team can work towards aligning risk management efforts with the overall business strategy, ensuring that risk is being managed in a way that supports the company's objectives.

The ERM framework does not necessarily allow the company to determine and make use of a higher risk appetite (option A), as risk appetite is a separate concept that is defined by the company's board and senior management. It is about the level of risk the company is willing to accept in pursuit of its strategic objectives.

Option B is incorrect because ERM promotes a unified approach to risk management rather than finding an optimal reporting methodology for each risk function in isolation. The goal is to have a comprehensive view of risk across the organization, not to fragment the approach.

Lastly, option D is incorrect because ERM is about taking a portfolio view of all risks, considering how they interact and aggregate, rather than focusing on individual risks in isolation. This approach helps the company to manage risk in a way that enhances overall business performance, rather than just looking at standalone opportunities.

In conclusion, the key benefit of establishing an ERM framework, as indicated by option C, is the improvement in top-down communication and coordination within the company, which leads to a more efficient and effective risk management process.