Workbench meshing automatically updates and increases relevance

I am doing a comparative study, which means I have 2 very similar models, but with some small differences in geometry. I would really like to have identical mesh, as the differences are quite small and the results will be affected. However, in one of the 2 models, Meshing automatically updates into a higher relevance, with the results that one model has finer mesh than the other. Normally I would refine the other mesh, but it's already a long and heavy analysis and I would like to keep the coarser mesh. I don't have many mesh controls.

Does anyone know what prompts Meshing to refine? And if it doesn't in one model, why the other? The differences are a few mm, in a much larger model.