31 to 32 inches is tossed around often. you will discover that a proper stool will help [even be necessary] to use the bench correctly. it is imperative you have correct posture and are comfortable to squeeze the most out of your shooting.
i see a lot of shooters with poor posture. my stepson was always saying he needed to be very upright to absorb recoil. his groups shrank when i got him in position correctly. he was quite sure it would not help and would cause him pain or problems in some way. a year later he commented that it was a huge help in his shooting.
I run 31.5" just because that's what I had laying around and made a portable bench out of it. I often get complaints that it is too short, works out great for me with a short stool. The way I see it is if you can't get comfy on a steel table with proper sandbags/shooting rest then you sure as chit aint going to get comfortable out in the field. I watch in amazement when my friends try to use my setup: They struggle to get into the right position and then muff up the shot because they say they can't get comfortable but these are guys that have to shoot at game off of a steady rest. One friend won't shoot unless he's sitting or kneeling or has the gun on a rock steady rest of some sort. Cracks me up!!!
This table is older than me and built very well.