I have a very slow Internet connection (5 Mbps down, and even less for upload). Given that, I always download movies at 720p, since they have low file size, which means I can download them more quickly. Also, I don’t notice much of a difference between 1080p and 720p. As for 4K, because I don’t have a screen that can display 4K, I consider it to be one of the biggest disk space wasters.
Am I the only one who has this opinion?
Simple explanation, the higher the bitrate, the more data is dedicated to each frame to be displayed, so the higher the quality of each frame assuming the same resolution. This means fewer artifacts/less blocking, less color banding, etc.
Lower bitrate is the opposite, basically. The video is more compressed, and in the process it throws out as much information as possible while trying to maintain acceptable quality. The lower the bitrate, the more information is thrown out for the sake of a smaller filesize.
Resolution is the biggest factor that affects picture quality at the same bitrate. A 1080p video has a quarter of the resolution of a 2160p video, so it takes much less data to maintain a high quality picture.