If you search for either of the above terms in Wikipedia, you are redirected to the article on Isochrony. This is, on the whole, a fair summary of what most people say on the subject. What it lacks, as far as I am concerned, is any mention of David Abercrombie's contributions to the subject, and an explanation of Rebecca Dauer's approach proposing a stress-timed to syllable-timed continuum. I intend to put this right in the next few days.
A blog that discusses problems in Wikipedia's coverage of Phonetics
Emeritus Professor of Phonetics