Apple Watch SE 3 vs Galaxy Watch9

The phone the watch needs. Apple Watch works only with an iPhone. Galaxy Watch4 and later work only with an Android phone that has Google Mobile Services.

You cannot set up an Apple Watch with an Android phone or a Galaxy Watch with an iPhone, so this row decides the choice before any other.

Matters most if: You are deciding between an Apple Watch and a Galaxy Watch: check which phone you have first.

Apple publishes each security update and which watches it is for. Samsung lists the watches it still gives security updates to, quarterly at most.

On the Apple Watch side you see the latest update Apple has released for the newest watchOS that watch can run; on the Galaxy Watch side, whether Samsung still lists the watch. They are different kinds of information, so neither is marked as a gain or a loss.

Matters most if: You plan to keep the watch for years, or you are buying one used.

A promise of how long the watch will get software updates, in the maker's words.

Samsung announced up to four years of One UI Watch and Wear OS updates for Galaxy Watch4 and later models. Apple makes no such promise for Apple Watch, so its side says "Not published by Apple".

The main processor, by each maker's name: Apple's S chips, and Samsung's Exynos or Qualcomm's Snapdragon chips in Galaxy Watch.

The names come from different makers, so the row shows both without picking a faster one.

Space for apps, music and other things saved on the watch, in GB (gigabytes).

Both makers give storage in GB, so more storage counts as a gain.

RAM is the watch's working memory for the apps running right now, in GB (gigabytes).

Samsung lists RAM for each Galaxy Watch. Apple does not publish it for Apple Watch, so the Apple Watch side says "Not published by Apple" and the site does not estimate it.

Each maker's lowest US price when the watch came out, before sales tax.

Apple's figure is its list price; Samsung's is usually the "starts at" price from its announcement. When the two are different kinds of price, the page says so and does not show the difference.

Each maker's own name for the screen: Apple's LTPO OLED screens and Samsung's Super AMOLED screens.

A name alone does not tell you which screen is better, so the row is marked "Different" without a winner.

How bright the screen can get at most, in nits (a unit of brightness), as each maker states it.

A brighter screen is easier to read in direct sunlight. Where Samsung says a figure is only a peak in part of the screen, the two are not counted as a gain or a loss.

An ECG (electrocardiogram) records the electrical signals of your heartbeat, here from your wrist and a fingertip.

Both makers' ECG apps check the recording for atrial fibrillation (AFib). Samsung's needs the Samsung Health Monitor app, which needs a Galaxy phone. Availability varies by country.

Apple's Hypertension Notifications look for signs of high blood pressure over time and tell you if they find them. Samsung's Blood Pressure takes readings, after you calibrate the watch with a cuff every four weeks.

They are different kinds of features, so the row shows both without a gain or a loss. Samsung says its feature cannot diagnose hypertension. Availability varies by country.

Matters most if: You want to keep an eye on your blood pressure.

Each maker's own battery figure. Apple gives hours of typical use; Samsung gives a figure for only some models.

The tests are different, so the hours can't be compared directly and the site shows both without picking a winner.

Matters most if: You want to wear the watch overnight or on long trips.

mAh (milliamp-hours) measures how much charge a battery holds, like the size of a fuel tank.

Samsung gives a capacity for each case size. Apple does not publish one for Apple Watch, so its side says "Not published by Apple".

The sizes the watch comes in, measured across the case in millimeters.

Within one model, the bigger case has the bigger screen and feels larger on the wrist. Try both sizes on if you can.

How heavy the watch is, as each maker gives it.

Apple gives the weight of the case for each version, and Samsung weighs its watches without the band, so the watch on your wrist weighs more than either figure.

How well the watch resists water and dust, in each maker's own ratings. Apple: water resistance in meters (WR50, WR100) and IP6X dust resistance. Samsung: 5ATM or 10ATM and IP68, and on Galaxy Watch Ultra2 IP69K.

The two makers use different tests, so the ratings are shown side by side and not ranked. Both say water resistance is not permanent and can get weaker over time.

Matters most if: You swim or dive with your watch.