OnePlus 9 vs Samsung Galaxy S21: which should you buy?

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You see the odd sacrifice here and there. They aren’t made entirely of glass and metal, and they don’t have cameras quite as advanced as the top Samsung and OnePlus phones. But you do get to save at least a couple of hundred pounds, and what you lose will not be all that glaring to most people.

But which is best? The Samsung Galaxy S21 is, we think, a prettier phone. It takes better zoom photos and is one of the very best ‘small’ phones you can buy.

The OnePlus 9 costs a little less, is more powerful and the larger screen is great for games and video streaming. There’s no clear all-out winner here, but stack up your priorities, and this shouldn’t be too tricky a choice.

For another comparison piece, take a look at our iPhone 12 vs Samsung Galaxy S21 article. To see how the OnePlus 9's big brother compares to another rival, don't miss our OnePlus 9 Pro vs Oppo Find X3 Pro explainer. And for our comprehensive breakdown of the Galaxy handset range, there's our Samsung Galaxy Phones list article.

Jump to:

Key differences at a glance
Specs and features
Price
Battery life
Camera
Display
5G capability and connectivity
Design
Verdict: which should you buy?

OnePlus 9 vs Samsung Galaxy S21: key differences at a glance

The OnePlus 9 has a larger screen, useful for playing games and video
Samsung’s Galaxy S21 has a much better zoom camera mode
The OnePlus 9 has a better processor, one that makes games like Fortnite run slightly faster
A Samsung Galaxy S21 is a better choice if you want a small phone, as the OnePlus 9 is significantly taller and wider
The OnePlus 9’s battery charges much faster, but those who use their phone quite a bit will have to recharge every day with either
Samsung’s Galaxy S21 has excellent IP68 water resistance, but the OnePlus 9 has no rating – so no official water resistance

OnePlus 9 vs Samsung Galaxy S21 in detail

OnePlus 9 vs Samsung Galaxy S21: specs and features

These are high-end phones, even if they don’t cost £1,000. You don’t miss out on too many features with either.

They have 5G, fast charging, OLED screens and top-end processors. However, the OnePlus 9 is the more powerful phone, despite being a little cheaper.

It uses the Snapdragon 888, which is newer and better than the Samsung Exynos 2100 of the Galaxy S21. The difference is not obvious when you do low-level stuff but is quite clear when you run Fortnite, one of the most demanding Android games.

Each match starts with the player flying through the sky above the island play area, and the frame rate is significantly higher — and more stable – in the OnePlus 9.

The way these phones present Android is a little different too. The OnePlus skin is more like vanilla Android, with a zero-upkeep (optional) vertical app library screen. Samsung uses a series of pages on which your apps sit, so you’ll need to keep them organised for the best results.

That said, there is an option to auto-tidy them with a tap. If only we had that option for our homes.

OnePlus 9 vs Samsung Galaxy S21 size compared

OnePlus 9 vs Samsung Galaxy S21: price

If you assess these two phones by their recommended prices, the OnePlus 9 is significantly cheaper. It costs £629 with 128GB storage or £729 with 256GB.

The Samsung Galaxy S21 launched at £769 with 128GB storage, £819 with 256GB .

However, the Galaxy phone has been around for longer, and we have seen it drop to around £650-£680 online, just a little more than the OnePlus 9. If you decide to go with Samsung, shop around for the best price.

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OnePlus 9 vs Samsung Galaxy S21: battery life

Neither of these phones is a true battery life trooper, the sort of Android you can realistically expect to last two days between charges.

They should last a full day for most people, but you may want to give them a little top-up before a night out if you spend some time during the day scrolling through social media or watching YouTube.

The OnePlus 9 has a larger battery, 4500mAh, to the Galaxy S21’s 4000mAh. But don’t forget the Samsung also has a smaller screen.

In our experience, the OnePlus 9 lasts slightly longer than the Samsung, and it also has much better charging. Its adapter is more than twice as powerful, 65W to 25W. You don’t even get a charger plug with the Samsung Galaxy S21.

We charged the two from flat, and by the time the Galaxy S21 was up to 25%, the OnePlus 9 was already at 54%. You get 15W wireless charging with either phone, and the Samsung has reverse wireless charging. This is most useful for topping up sets of wireless earphones like Samsung’s Galaxy Buds.

OnePlus 9 vs Samsung Galaxy S21 compared

OnePlus 9 vs Samsung Galaxy S21: camera

Samsung is a master of phone cameras. But this year, OnePlus not only teamed up with photography icon Hasselblad to improve image quality, but it also used higher-end hardware in the OnePlus 9 than its last generation.

So which has the best camera? The OnePlus 9 and Samsung Galaxy S21 excel in different areas.

The Samsung Galaxy S21 has a much better zoom, handy for travel images and capturing dogs playing in the local park. It also fares a bit better at night, although both have useful modes dedicated to getting you clean-looking shots in low light.

Samsung also tends to make your images “pop” that bit more, brightening up the areas in a picture at risk of looking dingy. You’ll notice this when shooting sunsets or scenes with dramatic bright-but-cloudy skies.

However, the OnePlus 9 has a much sharper ultra-wide camera. This is no surprise, as it uses a very high-res 50-megapixel sensor.

Don’t expect a big variation in detail in images you take with the primary cameras, though. The OnePlus 9 may have a 48-megapixel sensor to the S21’s 12-megapixel one, but they capture similar levels of detail.

Who wins? The Samsung Galaxy S21 feels like a more flexible camera phone. Sometimes the OnePlus 9’s colour looks more natural, but we think more people will appreciate the added punch of Samsung’s pics more often.

Both phones can shoot video at up to a staggering 8K resolution, but 4K offers the best balance of compatibility, motion smoothing and image quality.

OnePlus 9 vs Samsung Galaxy S21: display

The OnePlus 9 has a larger screen than the Galaxy S21. It’s 6.55 inches across, to the S21’s 6.2 inches.

You’ll appreciate that extra space when watching video or playing games. An extra 0.35 inches may not sound like a lot, but it matters.

Their resolutions are the same, 2400 x 1080 pixels. That means the Galaxy S21 is actually slightly sharper per inch, but in person, they look similarly crisp.

The Galaxy S21 does have a couple of benefits. Its colour tone is more even at an angle, where the OnePlus 9 takes on a slight red tint. And it looks clearer in bright sunlight. This isn't just because the S21 has slightly higher peak brightness, which it does, but because Samsung does clever stuff with colour and contrast to keep it looking good in all conditions.

This is an unhelpful case where you win some, you lose some. A bigger screen is great, but Samsung’s display is slightly better-optimised in a few ways.

They are both OLED screens, which have flawless contrast, with a refresh rate of up to 120Hz for ultra-smooth scrolling in Android. There’s a fast fingerprints scanner built into both displays too.

OnePlus 9 vs Samsung Galaxy S21 display compared

OnePlus 9 vs Samsung Galaxy S21: 5G capability and connectivity

The OnePlus 9 and Samsung Galaxy S21 have 5G, one of the most important new bits of tech in recent years. They also support Wi-Fi 6, which will keep your phone up to speed with your home broadband router in the years to come.

Future-proofing is on-point.

Neither phone lets you plug in a pair of wired headphones, and neither takes a microSD card. Think carefully about the storage capacity you’ll need, then, because you can’t upgrade it.

OnePlus 9 vs Samsung Galaxy S21: design

The OnePlus 9 and Galaxy S21 offer high-end specs at a slightly more palatable price. And that means you have to swallow a little design compromise in each case.

Samsung uses plastic on the S21’s back instead of glass but keeps the aluminium sides seen in the more expensive Galaxy S21 Plus and Ultra.

OnePlus retains the glass but uses plastic on the sides. Which feels better? There’s not much in it, as while a drop from a glass rear to a plastic one is usually obvious, Samsung has done an excellent job making plastic feel fancy here. But the OnePlus 9 might snatch it by a whisker.

For the latest news and expert tips on getting the best deals this year, take a look at our Black Friday 2021 and Cyber Monday 2021 guides.

The Galaxy S21 is the more stylish phone, though. There’s real eye-catching confidence to the design of its camera housing and the two-tone colour scheme. It’s one of the best-looking phones Samsung has ever made.

Size is probably a more important difference here than style. The Samsung Galaxy S21 is a petite but powerful phone, a rare and desirable combo. The OnePlus 9 is significantly larger, much closer in size to the average flagship phone.

A bigger phone is worth it if you’re a big consumer of content, watching YouTube or Netflix, or playing games. But there’s a real charm to a smaller phone. It’s easier to handle, takes up less space in your pocket and shrugs off the nerdiness of high-end tech.