I suppose it’s all what you get used to but vertical or horizontal/vertical splitters wear my butt out, seem painfully slow to me, and the wedge is on the ram which just makes things harder. I don’t load my firewood until after it is split; I leave the mess laying in the woodlot that way.
I buck the rounds and toss, or roll into a pile, then I position the splitter in front of me with the pile behind me. I set a round on the beam and throw the lever (my splitter doesn’t require I hold the lever, fully auto cycle) and turn to get another round. The wedge is on the beam so splits are pushed off the end and don’t end up at my feet, in the way. When I get a pile of half splits at the end I reposition the splitter (mine only weighs 200 lbs so you can move it with one finger) so the pile of halves is behind me and the splitter and trailer are in front of me. Now I start splitting the halves, and because I don’t have to hold the lever I have both hands free to grab the two quarter splits coming off the end, and toss them in the trailer.
With a vertical splitter (yes, I have used one) the constant getting up from the “stool” to get another round just flat wears me out and the splits are always in the way. When I put a horizontal/vertical splitter in the horizontal position it is way too high, I have to lift large rounds all that distance, which wastes time and effort, wearing me out in a short time… and the splits fall/bounce/roll on, or around my feet because the wedge is on the ram. I have to bend over to pick up the rounds anyway so I prefer the beam about a foot or so off the ground… and it’s quite easy to lift/jerk/hook/roll a large round up onto the low beam, rounds larger than I could possibly pick up to waist height (you’d be surprised the size/weight of wood you can “jerk” onto a low beam, with relatively little energy expended).
Now I have split from the back of a pickup box or trailer on occasion (always smaller rounds because they had to be lifted and loaded at some point), and to eliminate the bending over I just put my (200 lb) splitter on three jack stands (which is easy because I can pick up either wheel or the beam end with one hand).