The big plus of ArchiCAD MEP Add-On - that in ArchiCAD it is possible to create your own library written on GDL. It is a complicated task - to program complex MEP objects on GDL, but the result is great. The big minus - MEP Add-On was not developed for many years, GDL variable structure of MEP objects is very strange, default GDL scripts and macros are very heavy. Also during IFC import ArchiCAD replacing straight pipes with ArchiCAD MEP native pipes (that later can be modified), but all bends and other elements - as static objects. It would be great if Graphisoft continues MEP Add-On development and introduce a new version of it. See attached examples, done by me using ArchiCAD MEP Add-On and custom GDL libraries.