1. A concise explanation of the problem you’re experiencing.
has anybody experience with PERFORMANCE tweaking when either using extruded ellipse or cylinder - etc - would one being better than the other?
superficial observation on iPhone iOS13 finds that the extruded ellipse variation would crash (easily)
although i would assume that extruded ellipse would provide better performance - just a hunch 
2. A minimal code example. If you’ve found a bug, this helps us reproduce and repair it.
no code needed i guess
or-
https://api.iidj.net/coronavirus/timeline (czml cylinder)
https://api.iidj.net/coronavirus/tiumeline_20200227 (czml extruded ellipse)
3. Context. Why do you need to do this? We might know a better way to accomplish your goal.
improve user experience when dealing with large sets of 3d objects
4. The Cesium version you’re using, your operating system and browser.
1.66
thanks for any experience/insight shared!