Service/subscription, list and recipient folders are all the same idea, grouping recipients together, and can be used interchangeably and in combination with each other.
Service is the most feature-rich, integrating with mobile apps and sub/unsub pages. Recipient lists I've seen used as a form of permanent temp table, stashing populations to be transferred between workflows; e.g. a workflow to select population, then a separate one to apply complex suppressions, then an execution workflow. Folders would be more organizational, defining fixed populations by region or whichever business case.
The recipient table hosts recipients irrespective of how they're grouped.