I will say I enjoy the topic and discussion, and believe it’s one that should be discussed openly and candidly.
It’s not a “topic” requiring discussion. It only required an answer. The question is an inquiry into the industry standard terms.
As a practical matter, when you see the terms Royalty Free Music and Stock Music, one might assume that they are the same thing. If not, how do they differ? For example, PTrax sells both Royalty Free and Stock Music. Because some of the titles and artists overlap it suggests that there’s potentially something different in how each is treated under its terms of use.
As Mark said: single use vs. pay once use forever. Question answered.
There isn’t meant to be an implied “which is better?” in the subject heading. “Royalty Free Music versus Stock Music: Which is Better?” would be a different topic.