It’s going to be display that I’m going plumb a frag tank to.Is this going to be a display tank or frag tank?
If display tank , I would definitely go with the 16" high option as you will have a bigger display to enjoy. I would go with 18" high if you have the option, even 16" is a little shallow for a display tank imo. You will also be able to have taller rock structures, and more length/height for the fish to swim.
If using as a frag tank I would go with the 12" high option, as you will be able to fit more frags with a bigger footprint.
Really depends on how you intend to use the tank.