I worked on both Atom and RSS Feeds for blogging engines. Frankly, Atom had for me no real advantage. RSS is easy to generate, and it is supported properly by so many clients that Atom can be comfortably ignored. Stuff like the guid not being a guid work in practice just fine.

To be honest, they're basically interchangeable. Most parsing libraries will handle both, and it's entirely down to preference.

But working on a blogging engine (producing feeds) or saying parsing libraries will handle it is just externalizing the problems with RSS to the consumers. That's where the real pain point is: understanding the content of an RSS feed, especially when thousands of feeds can have a multitude of different quirks.

From my [not extensive] research, ATOM open source libraries have better support for authenticated feeds.

The problem isn't generation, but consumption. If you're consuming feeds, Atom is significantly better than RSS because it's better specified.

Well they are both the same as a medium, that is apart from technical benefits to the producer and the consumer programmes, they are both easy, easy to implement, easy to publish, easy to (un)?subscribe and free of third-party involvement.