user12280: If I was to compare a 720p video encoded (using x264) from an untouched 1080p Blu-ray rip with the same video encoded at a similar bitrate but from a 1080p x264 rip, which one is more likely to look better in terms of perceived quality?

user26471: A lower-than-optimal bitrate video with higher resolution could easily look worst than a smaller one with proper bit per pixel dedication. Of course a very important fact is the viewing device and condition. A smaller video should get upscaled to fill the screen, for example a 1280×720 will get upscaled in full-screen mode on a 1920×1080 screen. 
So, in conclusion the perceptual quality highly depends also on other factors than the resolution only.

user1871: If the 1080p encode has a high enough bitrate, one shouldn't notice a significant difference, else the BD source offers greater headroom to retain detail.

12280: <p>If I was to compare a 720p video encoded (using x264) from an untouched 1080p Blu-ray rip with the same video encoded at a similar bitrate but from a 1080p x264 rip, which one is more likely to look better in terms of perceived quality?</p>
 26471: <p>A lower-than-optimal bitrate video with higher resolution could easily look worst than a smaller one with proper bit per pixel dedication. Of course a very important fact is the viewing device and condition. A smaller video should get upscaled to fill the screen, for example a 1280×720 will get upscaled in full-screen mode on a 1920×1080 screen. </p>

<p>So, in conclusion the perceptual quality highly depends also on other factors than the resolution only.</p>
 1871: <p>If the 1080p encode has a high enough bitrate, one shouldn't notice a significant difference, else the BD source offers greater headroom to retain detail.</p>
