Apple's current Watch lineup still splits along a familiar line: cheap and capable, or pricier and medically useful.
The Apple Watch SE 3 starts at $249; the Apple Watch Series 12 starts at $399. Both run the same watchOS features, always-on display, wrist temperature sensing, sleep apnea notifications, and 5G on cellular models. The $150 gap buys a newer S11 chip with double the RAM, a bigger and brighter LTPO3 display, a titanium or ceramic case option, and meaningfully more battery life, up to 24 hours versus 18, with faster charging too. It also buys health hardware the SE skips outright: an electrocardiogram, blood oxygen monitoring, hypertension notifications, and more frequent heart rate and HRV readings.
That split is really a question about what you use a smartwatch for. If notifications, basic workout tracking, and sleep data cover it, the SE 3 gets you there for $150 less, and nothing about the SE's slightly older chip makes it feel behind. The Series 12's extra sensors only pay off if you actually want to monitor heart rhythm or blood oxygen, features aimed at people managing or watching for a specific health condition rather than casual fitness tracking.
At $150 less, the SE 3 skips the ECG, blood oxygen sensor, and hypertension alerts entirely, a fair trade only if you never wanted your watch playing doctor.