If you are viewing a small file (a part, small assembly or even a small piece of infrastructure) it is likely that your viewing performance will be the same in either of the modes. However, if you are diving into larger models, you have two options for viewing the model - Progressive Model Display or the Regular Model Viewing.
To access these options, click on the settings icon in the viewer toolbar, and navigate to the 'Performance' tab. Then check or uncheck the "Progressive Model Display" Option. By default, the progressive model display option will be turned on.
Progressive Model Display - OFF
For most models, having progressive model display turned off will work very effectively. The model will not re-render as you move it and will manipulate effectively. If you find the model is moving slow as you manipulate it or walk through it, then we recommend testing out progressive model display.
Progressive Model Display - ON
Progressive Model Display is best used when the model is large and moves slowly. Although the model will take a half second to completely render, you will be able to manipulate the model as if it was a small model.