The basic job of the workbench is to provide a solid surface and ability to hold the workpiece in a useful position for the task at hand. The vise that gets the most use on my bench is made by Record and fitted with a leather lined wooden block. By using the wide block on the jaw, it is easier to exert enough holding pressure without crushing the workpiece.
But besides having a good vise setup, I find that having a rational game plan for sequencing cuts can eliminate difficulty holding while carving a seat, which is one of the major uses for a workbench in chairmaking.
I've never understood the thinking behind cutting out the seat shape first. All the best ways to hold the seat end up in the scrap bin! I prefer to cut out only the front of the seat, after drilling the holes. Then reaming, carving and banging the seat around can be done without damage to the tender surfaces of the finished seat.
Next I carve the bottom of the front of the seat and then clean up the bottom with a few plane strokes as shown below. In this photo, the bench dog and vise are doing the holding.
Finally, I cut off the extra material at the back of the seat and shave it to shape. This way, the seat is ready to be legged up immediately and I don't have to back track to clean up clamp marks and errant dings. I also don't waste any time trying to figure ways to hold a piece by the finished areas.
I was asked about the height of my workbench, and I promise to measure it, but really the number is irrelevant. The bench should fit you and the type of work that you plan to do. Most store bought modern benches are tall, figuring that routers etc... will be used the most. A bench for hand work such as planing should be low enough that the user can comfortably lean over it and get some real leverage on the tool. Obviously, this will be different for everyone. As much as the gorgeous benches in the books call to me, I prefer to let my workbench, and shop for that matter, evolve with my needs. I'd hate to make a workbench that looks great but can't keep up with me.
So, as usual, my take is to cobble something together and work with it for a while (like a decade) and to spend enough time creating a process that works with the simplest set up.