Duane gave a good answer. It depends on the press and the bench, and whether you want to sit or stand. I have two benches with three presses, but two inline fab mounts. The first bench is very tall, 41", with a Dillon 550 on a Dillon strong mount. There's no sitting here, you really need to stand to see down into the cases, and I'm tall at 6' 8".
The other bench is lower with a taller chair, so I have an inline fab 4" Micro mount for a Lee Classic Cast, and a flush mount for a Co-ax that has an IF short handle. The handle of the co-ax is significantly taller than the Lee handle, and I want to reach out to it, not upwards each time. The offsets work for me so I can sit at both presses. If I want to stand at the Co-ax I would just move it to the 4" mount (and optionally change the handle back to stock.)
I have one extra flush mount on the other side of the bench to store a press on, or to use for a Dillon super swage 600 or a Lee bench priming tool, which are also on quick mounts, and those mounts are stored on the IF storage racks.
First measure the height of your bench, and if possible set your press up to get your handle height, then decide if you want to stand or sit or both. You want the height of inline fab riser that will allow you to reach out at shoulder height or perhaps down a bit to operate the press handle. At least that's what works for me.