First, it takes care of downloading video from sites such as Youtube and Vimeo. Often the online video downloaders like Video Downloader Professional are not reliable. They either won’t download Youtube videos at all, or if they do download them, you’re stuck with the resolution they choose. 4K Video Downloader solves that problem. You can specify various quality resolutions from 240p to 1080p, specify “Original” native resolution, or even, for reasons unknown to me, go with the super-low quality QCIF (176p). If the original video is 720p and you choose the higher 1080p, the video might not look that much better originally, but would probably stand up better to enhancement in a video editor.
Also, let’s not forget that these online downloaders have axes to grind and you may end up downloading something else along with your video.
Secondly, the program solves the issue of extracting audio from video clips on places like Youtube. Again, the online audio extraction services are unreliable in two respects: (a) they come and they go. What you use today may be gone in two months, and (b) you settle for the MP3 resolution they give you, which is often 128 kbit/s. The maximum 4K Video Downloader allows is indeed the hightest: 320 kbit/s. This opens up a world of music to you, probably more than you can listen to in a lifetime.
With both components you can also specify a default download directory. Excellent program.