For Screencastify the screencasting occurs at 25 frames per second, web cam activated, and audio recording. For Kazam the screencasting is recorded at 29 frames per second, a third party webcam app, and audio recording. All in all pretty comparable to test the performance of a cloud app vs a native app. For both test we will load Lubuntu in VirtualBox.
So here is what happened.
Screencastify not Screencaster. I have never used Screencaster.
Screencastify did a little better than I predicted. In an earlier test at 720HD recording, the audio distortion was noticable after a few minutes. In the test above there were two instances where audio was distorted for a few seconds. As far as the webcam it recorded both on the desktop and the VirtualBox session.
Kazam had better performance with the webcam app. The audio was better and the webcam video had slightly better quality. What was disappointing was even though I set it to always be on top, when we were in the VirtualBox session the webcam disappeared.
While Kazam was noticably better in audio quality, Screencastify was certainly in the acceptable range for performance. I had Screencastify on the highest casting setting which could be lowered if needed. If one did not have access to a native app or lacked the right codecs, Screencastify would certainly do an acceptable job.
Screencastify and Vokuscreen both have embedded webcam functionality. That is a feature I really miss in Kazam and one I hope the deleopers add soon. When I screencasted a VirtualBox session I lost all access to my webcam eventhough I set it to always be on top.
I guess the factors that need to be weighed are the lower video / sound quality in Screencastify and the lack of webcam support in Kazam. Right now it is tilting towards Kazam and a native Linux app, but the lack of an embedded webcam continues to be frustrating.