I've been going through this myself recently. I think the answer is "what ever height is comfortable for you". Too low can be a pain because you'll always be bending over or crawling on your back to get to the underside, too high can be a pain because you have to step up on something to reach or even see the layout.
Average counter top height is 36". When I searched this topic it seemed that 39 - 41" was an average recommended height. I'm average height, 5' 10", so I was planning for 38-39 myself but after dealing with leveling a few benches in my basement I seem to have ended up around 41" before any surface and homosote. Still workable for me but toward the high side in my mind.