RSS Feeds: Using Aggregator (Drupal Core) vs Feeds module - which has more features and is more reliable?
Answering my own question, I would be inclined to say Feeds module, on the basis of:


more integration with other Drupal entities allowing more possibilities for manipulation of the content
extensibility - ability to extend with extension modules that parse the XML content of the feed to re-purpose it. e.g. rather than a text list of youtube videos, the actual videos themselves embedded into the page
standard api for extensions
well supported and active in drupal 7