Gear 2 and Gear 2 Neo fitness functions are similar: Both respond to voice commands with S Voice when you can't easily touch the watch during a workout. You can also set goals for a fitness plan, which can be enhanced with connections to the S Health app shown here (and others from third parties) on the smartphone. Apps that combine GPS tracking from the smartphone with vital measurements from a run can be stored for future reference.
The devices are also dust and water resistant, but there's no rating for resistance to drops and other shocks. If fitness doesn't interest you, both can be used as TV controllers, and all three Samsung wearables can be used to find your connected smartphone.