If the LAS Dataset is being visualized in a global scene, then all the points being projected takes longer - and that is a known limitation. For the fastest performance in ArcGIS Pro, use a local scene and make sure its spatial reference is set to the LAS dataset's. Even in a local scene, ArcGIS Pro is somewhat slower to start rendering because it is creating a visualization cache. The benefit with ArcGIS Pro is that users can zoom in anywhere on a huge dataset (hundreds of millions/billions) and see in full detail. This workflow is tested in ArcGIS Pro 2.2.4 and ArcGIS Pro 2.2.2, with a local scene set with coordinate system of the data. The initial load was a bit slower to render point clouds with RGB. However, after the initial load and zooming and panning around, the points load quickly and renders fine.