Click this article about Blu-ray vs. 4K, and find out their main distinction. Afterward, choosing between Blu-ray and 4K will never be too hard for you.
Blu-ray Resolution: 4K and 1080p Full High-Definition Explained
What is Resolution of Monitor? Full HD vs 2K vs 4K
Blu-ray vs 4K: Difference between Blu-ray and 4K »
Guardians of the Galaxy Volume 3 [4K UHD + Blu-ray] : Chris Pratt, Chukwudi Iwuji, Bradley Cooper, Zoe Saldana, James Gunn: Movies & TV
Streaming vs UHD Blu Ray : r/4kbluray
4K VS Blu-ray VS 4K Blu-ray: Understanding the Differences
Blu-ray Versus - Alien (2010 vs 2019) 8K ULTRA HD Comparison
Archimago's Musings: 1080P Blu-Ray vs. 4K UHD Blu-Ray: Blade Runner (Final Cut) - Classic 35mm Filmmaking
What is a 4K Ultra HD Blu-ray Disc?