Why should I use a flat head vs. protruded head with the Soft Zoom Reflector?

The Soft Zoom Reflectors are compatible with both flat fronts and protruded heads and enable a wide range of effects with both. It is up to the creative to use the light that you get the light stamp of preference. In short, with both lights you can create both soft and hard light, a protruded head will generate a slightly more spread to the light while a flat front creates a harder light stamp when zoomed in. 

If you want to know more about the light effects of different flashes together with the Soft Zoom Reflectors, make sure to watch this Geared Up episode with Chris Fain: https://vimeo.com/846062472