I am not a Revit user, but I tend to think RFAs work a bit like using “macros” inside Revit, and I am sure if we try, we will find many aspects that might be better than using GDL. In the other hand, GDL is a truelly simple/accessible yet powerfull programming language. It allows you to to do objects like furniture, but also other kind of utilities, from importing and placing XL tables, to creating automated material maps, construction systems, configurators, etc. I also underline the reduced file size you get by using it. For instance, for internal use on an architectural project, at some point we developed a single GDL object that reproduced every possible option available for a bookshelf from IKEA catalog. I believe we are talking hundreds, if not thousands of different possibilities in a single simple object, including availability in different colors, position for each of the 2 or 4 shelves, (depending on the selected models etc). If I am not mistaken, its size was under 100k. We also developed it with a graphical user interface wich easily helped overlap language barriers, need for instructions, understanding of the library part or the original catalog.
(You can see it working here in a movie of our old website: http:///WZ8JjS8DqrQ )