Receiving systems can use sending IP behavior as one signal when deciding how to handle mail.
Useful observations can include complaint history, volume patterns, invalid-recipient traffic, abuse, authentication and historical behavior.
Shared and dedicated IPs
A shared IP combines traffic from multiple customers. A dedicated IP gives one sender more control, but also makes that sender responsible for establishing and maintaining its own history.
Neither is automatically better.
Reputation is receiver-specific
There is no universal Internet reputation score. Different receivers have different data and policies.