The Apple Watch 3 is an expensive one, but it’s full-featured, with a built-in GPS chip, water proof with a very fast chipset and optionally LTE. The Apple Watch 2 does not have the LTE feature and also the chipset of Apple Watch 2 is different from that of 3. Those are the only two main differences between the two watches. However, Apple has stopped selling apple watch 2. But apple watch series 3 GPS is amazing. My brother is using it right now and he loves it.