From Workspace Sample Time

Let's say you have a single Simulink model with plant and controller, and another that just has the plant.

If you save outputs of plant&controller with to workspace blocks, add from workspace blocks to plant only model and run it with outputs of plant&controller, you might see differences between results. In order to have a close match of results, you shouldn't leave the sample time of from workspace blocks as zero, you have to enter them equal to sample time of plant&controller model.