When switching between windows while in Simulate mode the performance is poor. This is because the moment you switch between models that Simulate creates simulation geometry which affects the loading. The problem is that the simulation geometry is cleared when you exit the window. This means that the simulation geometry has to be re-created when you switch back to a component that has in fact previousmly been loaded.
This is less of a problem when working with Simulate integrated with Creo Parametric, as you can close the Simulate Application, and switch windows in Creo Parametric.
However, in the case of the Simulation Standalone Application this becomes a bigger problem.
What I would suggest is that a type of smart regeneration be implemented that caches or keeps already loaded simulation geometry in session.
Otherwise, an improvement of the performance when switching would also be beneficial.