I have no idea what other capabilities you are talking about. This is about DRM. What Firefox features would web sites use instead of DRM? To your second point

I have no idea what other capabilities you are talking about. This is about DRM. What Firefox features would web sites use instead of DRM? To your second point: If you install IE or Chrome the DRM system will be part of your browser and you have something out of your control running on your system whether you want to watch DRMed content or not. With Firefox you can just keep using the web, and as long as you never want to watch any DRMed content, nothing changes for you. Only if you want to watch DRMed content will you be asked to download a plugin. As the cherry on top, Firefox will not leak identfiable data about your video usage to DRM or content providers. Unfortunately Mozilla alone can't stand against the power of Google, Apple, Mircrosoft, Amazon, Netflix and others united in their desire to push DRM through, but if you can't see the difference between Mozilla and the others, I don't think there is anything I can say to change your mind.