Zero drop is great for the gym, explosive exercises and dynamic movements.
Zero drop functionally is excellent for foot health, posture, and biomechanics. It is stripping back all the support provided by most trainers. It will set your foot free and take you back to operating as you would as a premature Homosapien. Biomechanically, zero-drop will provide the maximum stability for you, but it will exercise your foot more than you are used to in a commonly supported trainer.

5mm drop is the mid-ground between barefoot functionality and commonly supported running trainers. Great for runners transitioning to barefoot and the gym, CrossFit, and walking.
5mm drop is a great transition configuration for those wanting to explore barefoot-style shoes. It will provide some cushion but still keep you close to the ground for improved stability.

This configuration is similar to traditionally designed trainers that you might use more often. 10mm drop is for running long distances and for those needing more cushion in the heel. Great for relaxing, working, walking, and performing. 10mm drop means your heel is 10mm above your toe height, if you include the sole thickness, your heel is about 13mm above ground level, decreasing stability and therefore not recommended for dynamic and explosive movements.