Dillon 450 here. Which you would mount at the same height as a 550, but probably not the same as a 550B, 650 or ... because of the mounting bases they have.
For me, my bench is 38" at the top. Why 38"? Because most of the time I'm standing, but may sometimes sit on a bar stool. I stand in front of the press, arms at my side, bend my right arm at the elbo straight out. That puts my hand right on top of the handle knob. And standing, I can cycle the handle all the way down with just arm motion. I'm right at 5' 8". If you're taller, I'd imagine you'd want the handle knob taller. If you're going to sit, you want to be able to move the arm full stroke without limitation from your chair or body.
My other (green) press sits a few inches lower, and most of the time, I sit while using it.
-Steve