Yeah I’d say that PlexAmp radio (a) requires a big local library and complete Sonic Analysis, and (b) is much more “lean forward” than Roon. When you teach it by clicking on “up next” it learns fairly quickly and can seem kind of magic even though you’re helping it more than you realize.
That’s why I put this feature request in, I think it is the core of the difference - part interface, part more data collected on expressed preference, Pat options available. If you agree, welcome your votes: