RSS and ATOM are completely interchangeable, the format does not matter here imo. If ATOM had completely took over and everyone used it now instead of closed platforms, I'd be happy. As it is my message would be "Use one of the two, these are the technical differences, in practice it does not matter as all readers support both".

That doesn’t mention either of what I think are the most important differences:

(a) That RSS doesn’t support relative URLs, whereas Atom supports xml:base. I think some clients support xml:base on RSS, but certainly not all, so all links should be converted to absolute in RSS for compatibility.

(b) That RSS titles are of an unspecified format and bodies are only mostly HTML, leading to things like angle brackets in titles being mangled in different and incompatible ways by different clients, and plain text bodies being unreliable (indicated by the <content:encoded> mess which is I think theoretically identical in semantics to <description>, but they felt the need to duplicate it because clients had made such a mess of <description> because RSS developed “organically” in the worst way). By contrast, Atom gets it all right, allowing you to specify in each case whether you’re providing text or HTML. (And HTML is useful in titles: things like <em> and <code> are completely reasonable, and it’s a crying shame that almost no content management systems support inline formatting in titles. But if you are converting to plain text and know you’re dealing with HTML, you can strip tags. I do wish it supported both, e.g. “You don’t need <code>cat</code>” and “You don’t need `cat`” so you get backticks if monospace formatting is denied you.)

RSS is a mess that should have been completely retired about fifteen years ago. If you’re doing podcasts you have to use RSS because Apple started doing podcasts a few months before Atom was finalised, and they’ve chosen to just keep layering hacks upon hacks, namespaces upon namespaces, duplication upon duplication, for the next 16 years, rather than ever switching to Atom which would have resolved a lot of that (and maybe worked to standardise other parts, rather than duplicating fields half a dozen times for RSS, Apple, Spotify, &c. &c.). But if you’re not doing podcasts, please let RSS die. As a term, too, in favour of just “feeds” or “web feeds”, because it’s harmful, leading to people only hearing of RSS and so implement RSS because they didn’t realise they should be implementing Atom.