Even if you start recording the same PowerPoint slides again, (e.g. you take a break during the class.) the newly recorded content must be saved as a separate project file. Therefore, to combine separate clips into a complete video, you need to use a complicated editing tool.
As for EverCam, in the same scenario, new recordings will be appended to previous ones without any further editing. Also, your recorded project will be saved automatically according to the path and the filename of the PowerPoint slides. This design makes the process of continue recording become very easy.