We link the models without exception. The shared model wasn't really an option until 2014 since anything before this required a discipline specific program (Revit Arch, Revit Structure, etc). I suppose with all of the programs now being included in the Suite, it's possible to share a model. However, I think we would be hard pressed to ever attempt to do this on any major project. Even with our best architectural clients, I am sure we would find their workflow and our workflow are too different to make the shared model work efficiently.
PE, SE
Eastern United States
"If a builder builds a house for someone, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death!"
~Code of Hammurabi