There's no FAA requirement to log "dual given" at all, so the choice is more a matter of convention than regulation. It's more a matter of what you plan to use it for.
If you are using "dual given" as a shorthand for "flight training given," the FAR defines that as in an aircraft. That the way most log it since it also counts as loggable "flight time."
Some include training in a simulator since it technically counts as "pilot time." I haven't heard of it being done but some might use a looser definition of "dual given" to include all "training time" whether flight training or not.
Since the FAA doesn't ask you to track it it doesn't matter that much.... except I can't imagine a use for it where you wouldn't want to break it down into its' ground, air, and simulator components.
btw, you can use dual given in a sim for one ATP requirement. 61.159(a) refers to "at least 1,500 hours of total time as a pilot." "Pilot time" does include training given in a simulator. Problem is that all of the subcategories of the ATP requirements involve "flight time." If you meet those requirements, it's unlikely that you will also need a few excess hours of non-flight "pilot time."
(All the definitions I mention are in FAR 1.1 and 61.1)