I would think ticket holders trend more towards deciding ahead of time to hop, but AP holders - since they can always hop - would be more inclined to decide in the moment where they want to go. I definitely think AP holders made spur of the moment choices.
The only thing is though, if a group is thinking about hopping, it pays to start stacking G+ well before arriving at the 2nd park. Otherwise they are missing out on prime options. If they wait until they are on the way to the 2nd park - say 5pm or later- not much is left to G+. If you start stacking passes at 2pm, then you can get some decent G+ for MK.
If one wants to make the most of G+, the only worthwhile hop is to go to MK in the PM though, because MK has the most rides, and is open the latest. by 2pm, there isn't much left in AK, HS or Epcot. All the good G+ rides are long gone.