While clicky switches (Blue, Green) provide audible feedback, they can be loud and distracting to others. Brown switches don't have any click, but still make a bit of sound because of the slight tactile bump.
A lighter pressure point means that you don't need to hit the keys as hard for it to register. For Brown switches, you can lightly tap the key and it will register, while other switches require more force.
With 80g of activation pressure, the Green switches are the heaviest available. If you find yourself pounding on your keyboard, yo're sure to like the weight of the Green switches.