Cesium world terrain vs google p3d tiles

between the two CWT vs google p3d tiles which one is more accurate in height at given lat lon?

which of this is ideal format for terrain quantized mesh or 3d tiles?

between the two CWT vs google p3d tiles which one is more accurate in height at given lat lon?

We believe Cesium World Terrain to be accurate relative to its data sources, which are documented here:

As far as I know, Google does not document the sources or accuracy of Google Photorealistic 3D Tiles.

which of this is ideal format for terrain quantized mesh or 3d tiles?

There are strengths and weaknesses to each. It might help to provide some context for the question. Are you considering generating one or the other yourself?