The Onshape screenshot is using SSAO (screenspace Ambient Occlusion) which is very common feature in Gaming Cards now.

Regardless, I am modeler....i prefer to see the surface, and SSAO will start to artifact when zooming in to small areas, which just mucks up the experience.

Transparency on the other hand, is a very useful feature for tracing surfaces and visualizing. Things like concepting a helmet are useful, if we can see the interior.

I'm definitely a +1 for adding Ambient Occlusion as a viewport option in Moi 4. When things look good, it only helps with the motivation! (..and the sales :))