What the heck, I'll weigh in.
For work surfaces, such as a vise, a hammer forming table or an anvil, the old blacksmiths used to set the top of the work surface even with their arm bent 90-degrees at the elbow. I have a dedicated vise table, and that's the height of the vise jaws, and it works great. I also have a hammer forming "station" for a shot bag, and that height works well.
For things that I'll be working AT, as opposed to working ON, I prefer it to be much higher. For instance, a floor-mount drill press, a hydraulic press or a bead blast cabinet. For all of these, I raise them 6 inches. (I'm 6-feet tall). This puts the work at an angle that doesn't require me to hunch over.
When I build my welding table, I'm not sure what height I'll have it... probably higher than the anvil height, because I won't want to bend over it. If I have a project that requires sitting, I'll pull up a stool.
For a bench, or counter along the wall (which you don't usually sit down to work at), I'd vote tall... belly button or higher, since you'll be standing there--and you don't want to stand there hunched over.
-Brad