I think there are a lot of right answers to the question, but as our goals have changed so have our ideas about how to achieve them.
We started with 10 fame Deeps and shallows for honey. Now I am buying/building nothing but deeps for the flexibility it affords when making splits, nucs, strengthening, etc.
We will continue to use the shallows on a few hives set aside for honey production but will not be adding more shallows to the inventory.
Each beek has reasons for selecting the equipment they use, and the beautiful thing is you can make anything work. Keep in mind the limitations on flexibility when selecting what you will use.