I let my table saw guide me as to the height and my "chop saw" determine the depth (I built-in an area to hold the 12" Miter/Chop Saw). The height allows me to use the bench and table saw top to support longer / wide items from time to time.
The idea, elsewhere of leaving a space below the top to store miscellaneous tools and such is a good one - improved by fixing drawers in the space so you can store stuff the full depth of the bench and still retrieve them. Taking this a step further, the space under the bench is best fitted with deep and wide drawers for the same reasons.
Design for a vise - retrofitting a vise is a royal pita and at least one vice is a great idea that wll get lots of use. The top of the vise jaws in the same plane as the bench top (or slightly 1/32-1/16" below) and at the right or left hand corner depending on your preference.
I built mine with a quarter-inch sheet of Masonite over top of the structural top material with the idea of replacing the top if/when needed.
I also built-in a power strip at the front edge of the bench so I don't have cables running over the bench top. Mine was a steel strip that allowed me to recess it into the front apron a few inches below the top. The cord for it ran underneath the top to the wall outlet behind the bench. (Actually, I have three of these on the apron - Left, Middle & Right because you can never have enough outlets.
If you're into hydraulics, you can do as a fellow I met in Florida and build a bench that can be raised or lowered - it was really cool. He could lower it so it was comfortable to sit and work or raise it when standing and working on a project! He also had re-worked his floor mounted drill press to oscillate the quill so he could use sanding drums with it.
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