OnePlus announced the OnePlus 9 and the 9 Pro during an event on 23 March, with an on sale date of 31 March.

You can read how the OnePlus 9 and 9 Pro compare to each other in our separate feature, but here we are looking at how the OnePlus 9 and 9 Pro compare to the Samsung Galaxy S21, S21+ and S21 Ultra

OnePlus 9 Pro 5G - 8G+128GB (Morning Mist)

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Design

  • OnePlus 9: 160 x 74.2 x 8.7mm, 192g
  • OnePlus 9 Pro: 163.2 x 73.6 x 8.7mm, 197g
  • S21: 151.7 x 71.2 x 7.9mm, 172g
  • S21+: 161.5 x 75.6 x 7.8mm, 202g
  • S21 Ultra: 165.1 x 75.6 x 8.9mm, 228g

The OnePlus 9 and 9 Pro both have a punch hole camera in the top left corner, but the 9 has a flat display and a plastic frame, while the 9 Pro has a slightly curved display and a metal frame.

Both devices have a prominent rectangular camera housing in the top left corner of their glass rears, with two stand out lenses. The 9 has a third smaller lens, while the 9 Pro has two additional smaller lenses. Both devices feature Hasselblad branding.

The Samsung Galaxy S21, S21+ and S21 Ultra all have a centralised punch hole camera at the top of their displays. The S21 and S21+ both have flat displays and plastic rears, while the S21 Ultra has a curved display and glass rear. All three Samsung devices have a metal frame. 

On the back, the S21, S21+ and S21 Ultra all have a rectangular camera housing that moulds into the frame, making for a slightly different design. There are three large lenses on all three devices, but the S21 Ultra has an additional fourth smaller lens.

The three Samsung devices are all IP68 water and dust resistant, but only the OnePlus 9 Pro is out of the two OnePlus devices. In terms of size, the Samsung Galaxy S21 is the smallest, followed by the OnePlus 9, S21+, OnePlus 9 Pro and the S21 Ultra is the largest.

Display

  • OnePlus 9: 6.55-inches, 2400 x 1080, 120Hz
  • OnePlus 9 Pro: 6.7-inches, 3216 x 1440, 1Hz-120Hz
  • S21: 6.2-inches, 2400 x 1080 pixels, 48-120Hz
  • S21+: 6.7-inches, 2400 x 1080 pixels, 48-120Hz
  • S21 Ultra: 6.8-inches, 3200 x 1440 pixels, 10-120Hz, S Pen

The OnePlus 9 has a 6.55-inch AMOLED display with a Full HD+ resolution for a pixel density of 402ppi. It has a 120Hz refresh rate, though this isn't adaptive, and it has an aspect ratio of 20:9. 

The OnePlus 9 Pro meanwhile, has a slightly larger 6.7-inch display with an AMOLED panel with LTPO. It offers a Quad HD+ resolution for a pixel density of 525ppi and an adaptive refresh rate between 1Hz and 120Hz. Its aspect ratio is 20.1:9.

The Samsung Galaxy S21 has a 6.2-inch Super AMOLED display, which makes it the smallest of the devices being compared in this feature. Like the OnePlus 9, it has a Full HD+ display, putting its pixel density at 424ppi. It has an adaptive refresh rate between 48Hz and 120Hz. 

The Galaxy S21+ has a 6.7-inch Super AMOLED display, like the OnePlus 9 Pro, but it has a Full HD+ resolution instead of a Quad HD+ resolution like the 9 Pro. This results in a pixel density of 393ppi, and like the S21, it has an adaptive refresh rate between 48Hz and 120Hz, so it doesn't drop quite as low as the 9 Pro.

The Galaxy S21 Ultra meanwhile, has a 6.8-inch Super AMOLED display with a Quad HD+ resolution for a pixel density of 516ppi. It offers an adaptive refresh rate between 10Hz and 120Hz, so still not as low as the 9 Pro, but it has support for Samsung's S Pen stylus.

Hardware and specs

  • OnePlus 9: Qualcomm Snapdragon 888, 8GB, 128GB/256GB, 4500mAh
  • OnePlus 9 Pro: Qualcomm Snapdragon 888, 8GB/12GB, 128GB/256GB, 4500mAh
  • S21: Qualcomm Snapdragon 888 or Exynos 2100, 8GB, 128/256GB, 4000mAh
  • S21+: Qualcomm Snapdragon 888 or Exynos 2100, 8GB, 128/256GB, 4800mAh
  • S21 Ultra: Qualcomm Snapdragon 888 or Exynos 2100, 12/16GB, 128/256/512GB, 5000mAh

Both the OnePlus 9 and OnePlus 9 Pro run on the Qualcomm Snapdragon 888 chipset, supported by 8GB or 12GB of RAM and with 128GB or 256GB of storage. Neither have microSD support for storage expansion. 

The two OnePlus devices both have a 4500mAh battery and both offer Warp Charge 65T fast charging. The OnePlus 9 has 15W wireless charging in Europe and North America, while the OnePlus 9 Pro has Warp Charge 50 Wireless, which is 50W wireless charging. 

The Samsung Galaxy S21 devices all run on either the Qualcomm Snapdragon 888 chipset or the Exynos 2100, region dependent. The S21 and S21+ are available with 8GB of RAM and either 128GB of storage or 256GB. The S21 Ultra comes with 12GB or 16GB of RAM and in 128GB, 256GB and 512GB storage options. Like OnePlus, none of the Samsung devices have microSD support. 

The Galaxy S21 has the smallest battery of the five devices being compared in this feature with a 4000mAh cell. The S21+ has a 4500mAh battery and the S21 Ultra has a 5000mAh. All three devices support for fast charging and wireless charging.

The five devices being compared in this feature all have under-display fingerprint sensors. They are also all 5G capable.

Samsung Galaxy S21 5G - 128GB (Gray)

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Camera

  • OnePlus 9: Triple (48MP + 50MP + 2MP), 16MP front camera
  • OnePlus 9 Pro: Quad rear (48MP + 50MP + 2MP + 8MP), 16MP front camera 
  • S21: Triple rear (12MP + 12MP + 64MP), 10MP front camera
  • S21+: Triple rear (12MP + 12MP + 64MP), 10MP front camera
  • S21 Ultra: Quad rear (108MP + 12MP + 10MP + 10MP), 40-megapixel front camera 

The OnePlus 9 has a triple rear camera made up of a 48-megapixel main camera with 1.12µm pixels and an aperture of f/1.8, a 50-megapixel ultra wide-angle camera with an aperture of f/2.2 and a 2-megapixel monochrome lens.

The OnePlus 9 Pro has a quad rear camera that offers the same three lenses as the OnePlus 9 but adds a 8-megapixel telephoto lens with an aperture of f/2.4 and 1.0µm pixels. Both the OnePlus 9 and the 9 Pro have a 16-megapixel front camera and both offer the Hasselblad partnership.

The S21 and S21+ both have a triple rear camera, made up of a 12-megapixel main sensor with 1.8µm pixel size, f/1.8 aperture and optical stabilisation (OIS), a 12-megapixel ultra-wide sensor with 1.4µm and f/2.2, and a 64-megapixel telephoto sensor with 0.8µm, f/2.0 and OIS. There's a 10-megapixel, 1.22µm, f/2.2 front camera.

The Galaxy S21 Ultra meanwhile, has a quad rear camera made up of a 108-megapixel main sensor with 0.8µm pixels, f/1.8 aperture, OIS and laser autofocus, a 12-megapixel ultra-wide sensor (1.4µm, f/2.2) and two 10-megapixel telephoto lenses, one with 1.22µm, f/2.4 (3x optical) and the other with 1.22µm, f/4.9 (10x optical). It also has a 40-megapixel selfie camera.

The three Samsung devices offer 4K 60fps video capture from all the cameras, with 8K 24fps offered on the rear too. The OnePlus 9 offers 4K video at 60fps and 8K at 30fps, while the OnePlus 9 Pro offers 4K at 120fps and 8K at 30fps.

Price

  • OnePlus 9 series: From £629
  • Samsung Galaxy S21 series: From £769

The OnePlus 9 comes in Winter Mist, Arctic Sky and Astral Black colour options. It starts at £629 in the UK. 

The OnePlus 9 Pro comes in Morning Mist, Stellar Black and Pine Green and starts at £829.

The Samsung Galaxy S21 starts at £769 in the UK and €849 in Europe. It comes in four colour options: Phantom Grey, Phantom Violet, Phantom Pink and Phantom White. The S21+ starts at £949 in the UK and €1049 in Europe. It comes in five colour options: Phantom Violet, Phantom Black, Phantom Silver, Phantom Gold and Phantom Red. 

The Samsung Galaxy S21 Ultra starts at £1149 in the UK and €1249 in Europe. It comes in five colour options: Phantom Black, Phantom Silver, Phantom Titanium, Phantom Navy and Phantom Brown.

Samsung Galaxy S21 Ultra 5G - 128GB (Black)

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Conclusion

The OnePlus 9 is the cheapest of the five handsets being compared in this feature, followed by the Galaxy S21 and then the OnePlus 9 Pro. The Galaxy S21 Ultra is the most expensive by £200 in the UK so budget will likely come into play when choosing between these handsets.

The hardware between the OnePlus 9 series and the Samsung Galaxy S21 series is similar, though the OnePlus 9 Pro and Samsung Galaxy S21 Ultra both offer more RAM as an option, as well as more storage in the case of the S21 Ultra. The Ultra also has a slighty larger battery capacity than the others, while the 9, 9 Pro and S21+ are identical.

The camera make up differs across the models, but the S21 Ultra delivers excellent results in our experience, and the S21 and S21+ are good too, while we found the OnePlus 9 Pro to be good, but a little inconsistent during our review. 

Ultimately, the decision between these devices will come down to budget and which features are most important to you. If you want the best camera, then the Samsung Galaxy S21 Ultra is probably your best bet, but if you want decent specs for a good price, OnePlus is on the money.