Your kitchen guy will be able to verify, but usually a single 42" cabinet is more efficient to construct and thus less expensive than two separate cabinets. I did 45.5" tall cabinets - 30.5" + 15", with inset doors, so doors are 26.5" and 12" tall (the face frames are extra wide on the bottom to hide plugmold and tall on the top for visual weight). I prefer glass in the top cabinets for reflecting light and for providing display space to store attractive things like vases, ceramic pots, etc., that are infrequently used.

Are you planning on having crown molding? Is your ceiling dead flat? Those are both reasons that 96” ceilings do not use 42” tall cabinets, or stacked cabinets.

A lot of it depends on your layout and how much storage you will have. I opted for double panel wood doors on either side of a 72" window so the focus would be on the view and not on the cabinet interior. I like opening a single door and seeing everything with no limitations on how the shelving can be adjusted. On the other side where there are no windows, I have two sets of 15" deep cabinets with full glass doors and LED lighting to store serving pieces and wine glasses. Glass cabinets can make a kitchen look bigger as the eye travels to the back of the cabinet.

A few examples:

Kepler Design · More Info

Fort Washington, PA · More Info

Monticello Replica · More Info