Samsung Galaxy S25 vs Galaxy S21: Is it worth the upgrade?

Whether you've been sticking with the Samsung Galaxy S21 since it launched or picked up one on discount in the years since then, chances are it's looking a little long in the tooth.

With the impending arrival of the new Samsung Galaxy S25, Galaxy S25 Plus and Galaxy S25 Ultra, it might be time to upgrade. If you're unsure where to start when it comes to teasing out the differences between this year's new Galaxy S25 devices and the Galaxy S21, here's what you need to know.

The Galaxy S25 and Galaxy S25 Plus rely on a 50MP wide angle lens, a 12MP ultrawide angle lens and a 10MP telephoto one. There's also a 12MP selfie shooter on the front. Then, the Galaxy S25 Ultra raises the stakes with a larger 200MP main sensor and 50MP ultrawide lens plus an extra 50MP telephoto lens.

That setup compares pretty favorably the one found on the Samsung Galaxy S21. Originally released in 2021, that device features a 16MP wide lens, a 64MP telephoto lens and a 12MP ultrawide lens. While that setup sounds pretty similar to the one on Samsung's latest lot of smartphones it's worth remembering that although the telephoto lens on the older device comes with more megapixels, it's limited by the capabilities of an older and smaller sensor.

Samsung's latest lot of devices also come with improved AI camera features like generative edits, instant slow-mo, best face (which is Samsung's take on Google's Best Take feature) and a new audio eraser (which is Samsung's take on Google's Magic Audio Eraser).

Samsung's latest lot of premium smartphones come with more (and more ambitious) AI features than ever. For context though, here's a full list of the various features and applications that comprise Samsung's Galaxy AI offering.

While Samsung has rolled out a few of these features to older Samsung Galaxy devices, the only things that have made their way back to the Galaxy S21 so far are Circle to Search and the ability to rewrite your text messages using generative AI. Safe to say, the myriad AI-powered apps and features here add up to one of the bigger differences between the Galaxy S21 and Galaxy S25.

Although both the Samsung Galaxy S25 and Galaxy S21 feature a 6.2-inch AMOLED screen with a 120Hz refresh rate and FHD resolution, there are a few key differences between the two when it comes to display and design.

Firstly, the more recent Galaxy S25 features a more advanced LTPO display panel. It's also got thinner bezels that add up to a 5% increase in screen-to-body ratio relative to its 2021 counterpart. The screen on the Galaxy S25 is also capable of 2600 nits at peak brightness, which is double the 1300 nits found on the Galaxy S21. The Galaxy S25 Plus and Galaxy S25 Ultra come with many of those same benefits, plus those that come with a larger 6.7-inch and 6.9-inch display panel.

In addition to having a better screen, the Galaxy S25 is also about 20g lighter than the Galaxy S21 and comes coated in Gorilla Glass Victus 2. Both devices come with IP68 rating for water and dust resistance, but that last detail indicates that the Galaxy S25 comes with more protection than the Gorilla Glass Victus found on the Galaxy S21 can offer.

Under the hood, the Samsung Galaxy S25 is powered by 12GB of RAM and a version of the Snapdragon 8 Elite chipset that's been tuned to take advantage of the larger vapor chamber inside Samsung's new smartphones. This silicon setup promises to offer a 40% improvement in NPU performance, a 37% improvement in CPU performance and a 30% improvement in GPU performance over what you could expect from the Galaxy S24 Ultra. Naturally, that more recent and powerful chipset is one of the biggest differences between Samsung's latest premium smartphone and the Galaxy S21.

Released in 2021, the Galaxy S21 runs on the Exynos 2100 chipset and 8GB of RAM. It struggled to keep up with the iPhone 12 at launch and the years since haven't done it many favors. When it comes to battery life, both devices feature a 4000mAh battery, so there's no major differences on that front. However, when it comes to software, it's the opposite story.

Samsung's new Galaxy S25, Galaxy S25 Plus and Galaxy S25 Ultra come with seven years of OS updates and seven years of security updates. Given that the Galaxy S21 is already past its use-by date when it comes to security updates, the more recent device easily walks away a winner here.