The Apple Watch SE 3 starts at $249, while the Apple Watch Series 12 begins at $399. The Series 12 offers advanced health sensing, a larger display, and extended battery life. Both watches share features like an always-on display, wrist temperature sensing, and sleep apnea notifications. The SE 3 retains the design of older Series models, while the Series 12 boasts a refined, thinner design with a larger, more immersive display. Case options differ, with the SE 3 limited to aluminum and the Series 12 offering aluminum, titanium, and ceramic. Screen durability varies, with the Series 12 featuring Ceramic Shield or sapphire crystal. Internally, the Series 12 has a more advanced S11 chip and double the RAM compared to the SE 3's S10 chip. Advanced health features like ECG, blood oxygen monitoring, and Vitals app with HRV are exclusive to the Series 12. Battery life is superior on the Series 12, offering more hours of use and faster charging. The Series 12 also includes Precision Finding for iPhones and enhanced audio intelligence features. For basic notification and workout tracking, the SE 3 is a solid value; however, for comprehensive health monitoring and premium features, the Series 12 justifies its higher cost.