Blu-ray and 4K are totally different concepts but when used in DVDs they can be compared together.
Sony UBP-X700/M, 4k Blu Ray Player For TV with Ultra HD Vision, HDR, WiFi for Streaming Netflix, or Disney+ & more. Includes HDMI Cable, Remote Control, Bluray/DVD Disc Cleaner, Cleaning Cloth
The Case for and against 4K
Titanic 4K UHD (1997) - Page 96 - Blu-ray Forum
The Mummy Returns [Blu-ray] : Brendan Fraser, Arnold Vosloo, Dwayne 'The Rock' Johnson, Rachel Weisz, John Hannah, Oded Fehr, Patricia Velasquez, Freddie Boath, Alun Armstrong, Adewale Akinnuoye-Agbaje, Stephen Sommers, James Jacks
Batman 4K UHD (1989) (30th Anniversary Edition) - Page 127 - Blu-ray Forum
The Ultimate Viewing Experience: Blu-Ray Vs DVD Vs 4K Vs 4K Ultra HD
Archimago's Musings: 1080P Blu-Ray vs. 4K UHD Blu-Ray: The Prestige - Modern 35mm Filmmaking
The 4 Best 4K Blu-Ray Players in 2021: Sony, LG, Panasonic, PS5
Why owning a 4K Blu-ray player is both smart and stupid
4K vs. 1080p: What's the Difference Between 4K and 1080p?
Best 4K Blu-ray players 2024: top picks for Ultra HD discs
What's the difference between 4K and Blu Ray mastered in 4K? : r/4kbluray
Is There a Difference Between SD, HD, and 4K?
