More accurate and reliable
Your smartwatch can probably do what the Coros Pod 2 can i.e. track your pace, distance, and location. But Coros claims the Pod 2 can do it better. It has an advanced accelerometer and can be clipped to your shoe for a more responsive pace data eliminating the 10-second delay usually seen on wrist-mounted GPS watches. This allows ensures that you stay within your targeted pace almost in real-time even without a GPS signal. It also measures your exact running distance even when indoors using the motion of your foot.
Instead of relying solely on GPS, the Pod 2 uses multiple internal sensors to compensate for GPS disruptions. Unlike a GPS watch, because of the position the Pod is clipped to, it can provide more running insights to help understand your running gait, form, and technique. Running insights include stride height, left-foot/right-foot balance, ground contact time, and stride ratio. Because it only weighs 5.6g it's hardly noticeable when you wear it.
There's also something Coros calls Effort Pace. It's a unique metric that tells you how hard you're working on a hilly terrain. It helps you to make decisions on pacing and analyze your overall exertion at the end of the workout.
Unfortunately it's only compatible with Coros wathes.