Optimization

If I have a DVD rip and a Blu-ray rip and want to optimize then both how, when the movies are identical, does Plex know which to do to 1080p and which to 480p? Out does it simply use the best quality version as it’s source?

I assume Plex would optimize the highest quality rip to whatever setting you want; a blu-ray rip optimized at 4Mbps will look better than a DVD optimized at the same setting…

Why would you want Plex to use the DVD as its source?