That depends on what you need. Do you need to always maintain the same height to the ground? If that is what you need then terrain following is the right choice.
If you don’t want to always maintain the same height to the ground and have a flat terrain (and aren’t flying at high speed) you can use the EK2_RNG_USE_HGT option which should give EKF a more accurate height.
These two options overlap on some scenarios, which is why it’s not easy to say what you should or not be using.