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Global Score
Basic Information
Android 11Android 11, 10
6.50 x 2.98 x 0.35 inches6.24 x 2.90 x 0.31 inches
8.04 ounces6.07 ounces
Phantom black and SilverPrism Crush black, Prism Crush blue, Prism Crush pink and Prism Crush white
Aluminum and Glass (Corning Gorilla Glass Victus)Plastic and Plastic
Scratch-Resistant GlassScratch-Resistant Glass
$ 966.00$ 282.00
Display / Screen
6.8 inches6.5 inches
3200 x 1440 pixels 2400 x 1080 pixels
516 pixels per inch405 pixels per inch
1500 cd/m2 brightness--
No touch screenNo touch screen
Qualcomm Snapdragon 888 chipsetSamsung Exynos 9611 chipset
Kryo 680, 64-bit, 5 nm (Octa-Core 2840 MHz) processorARM Cortex-A73 and ARM Cortex-A53, 64-bit, 10 nm (Octa-Core 2300 MHz) processor
Adreno 660 GPUMali-G72 MP3 GPU
128 GB internal memory128 GB internal memory
No SD card slotmicroSDXC (up to 512 GB) external memory slot
108.00 MP + 40.00 MP48.00 MP + 32.00 MP
f/1.80 aperturef/2.00 aperture
24.00mm focal length26.00mm focal length
0.75 inches (1/1.33") sensor0.5 inches (1/2") sensor
7680 x 4320 (24 fps) video resolution3840 x 2160 (30 fps) (4K) video resolution
1280 x 720 (960 fps) (HD) slow motion video1280 x 720 (240 fps) (HD) slow motion video
Mobile HotspotMobile Hotspot
5G, 5G, LTE-A (4G), LTE (4G), HSPA+ (4G), HSDPA and HSUPALTE-A (4G), LTE (4G), HSPA+ (4G), HSDPA and HSUPA
Nano SIMNano SIM, Dual SIM
Battery Life
5000mAh Li - Polymer Battery4000mAh Li - Polymer Battery
Non-Removable BatteryNon-Removable Battery
Wireless Charging--
Other Features
Bluetooth 5.1 Bluetooth 5.0
Fingerprint ID ScannerFingerprint ID Scanner
Accelerometer, Barometer, Compass, Gyroscope, Light Sensor and Proximity SensorAccelerometer, Compass, Gyroscope, Light Sensor and Proximity Sensor
FM RadioFM Radio

Comparison review

Samsung Galaxy S21 Ultra has a global score of 11.67, which is much better than Samsung Galaxy A51's 10.18 global score. Samsung Galaxy S21 Ultra is a newer phone than the Samsung Galaxy A51, but it is heavier and somewhat thicker. Both of these devices come with the same Android 11 OS (Operating System), so both of them should give you identical OS features.

Galaxy S21 Ultra counts with a much better looking screen than Samsung Galaxy A51, because it has a better resolution of 1440 x 3200px, a bit bigger screen and a greater pixels density. Galaxy A51 features much more memory to install games and applications than Samsung Galaxy S21 Ultra, and although they both have exactly the same 128 GB internal memory, the Galaxy A51 also has a SD memory slot that allows a maximum of 512 GB.

Galaxy S21 Ultra features a bit better processor than Galaxy A51, and although they both have 8 cpu cores, the Galaxy S21 Ultra also has a greater amount of RAM. The Galaxy S21 Ultra takes better pictures and videos than Galaxy A51, because it has a much bigger back camera sensor taking way higher quality videos and pictures, a back camera with a much higher 108 MP resolution, a bigger camera aperture to capture better low light images and video and a way higher 7680x4320 video definition.

The Galaxy S21 Ultra features a little longer battery lifetime than Galaxy A51, because it has 5000mAh of battery capacity.

Although Samsung Galaxy S21 Ultra is a better device, it is way more expensive than Galaxy A51, and it doesn't have such a good quality/price relation as the Galaxy A51. So if you want that extra specs and features, you can buy Samsung Galaxy S21 Ultra, otherwise you can save some dollars and get the Galaxy A51, resigning some features and specifications.