Hopefully, this article has shown you, in detail that there are some major differences. The TL;DR is this. The second iteration of the Apple Watch was significantly speedier than the original. The new Apple Watch Series 3 is even more rapid than its predecessor. The Apple Watch Series 3 is up to 70% faster than the Series 2 thanks to the W2 chip and upgraded dual processor. This improves the performance and lifespan of apps. Apple's breakdown demonstrates that the three versions still on the market have a lot in common. In spite of this, there are some notable differences between the Apple Watch SE and the Apple Watch Series 3, such as the larger display, Fall Detection, and the altimeter that is always on in the Apple Watch Series 3.