The big plus with using paragraph tags is that you are defining general rules with exceptions, so can make global changes.
For example, if you have been breaking at Heading 1 and Heading 2, but want to add breaks for Heading 3, it's one change in RoboHelp, plus applying Heading 3 Nobreak in FrameMaker for the topics where you don't want breaks. With markers, you'd have to add a marker for every Heading 3 except those where you don't want breaks. General rules are not enforced by the application so there's no way to make global changes. In the long run, I think that would be a lot of unnecessary extra maintenance work and over time you'd be likely to accumulate errors as a document passes through the hands of various authors and editors. Using paragraph tags also makes it faster and easier to see how any individual heading is set or change it.
