Mainframe modernization vs replatforming: which is better for enterprise systems?

Exploring Mainframe Modernization Strategies

I recently asked a technical question on Stack Overflow:

Topic:
Mainframe modernization vs replatforming – which is better for enterprise systems?

Looking for insights on:
Technical differences

Cost vs performance

Risk and scalability

Real-world implementation experience

Would love to hear perspectives from professionals working with legacy systems and cloud migration.