I will say this, if you dont have anything to lift big rounds, then vertical is the only way to go. When I got back into burning wood, I rented a speeco vertical/horzonal splitter. I found that those really large rounds just didnt fit on the foot plate and I had to twist and pull a bunch of wood in order to get the wood split. Also every split I had to toss to the side as soon as it was split, often one handed, and this tired me out quickly. I never liked noodleing big rounds, always used a 55 huskey as my firewood saw. Not the best saw choice for noodleing. I do noddle some of my bigger rounds, my boom will only lift about a 48in dia round up high enough to clear the splitter beam and my log dogs dont like grabbing/holding onto that size wood. I have acquired a couple of bigger saws over the years.
When I built my own splitter, I built it horizonal. I wanted a 4way wedge and wanted it to be adjustable height. I built the blade type wedge tall enough to make a clean cut thru a 24in dia round. None of that splitting a big round and having it to only be half split and hanging on top of the wedge. I learnt the 4way didnt always have to hit in the middle of the big round, raising it just high enough to make 2 small splits at the bottom of the round and leaving 2 larger splits on the top half of the round. This allowed me to stack the two larger pieces on top of each other and run thru the wedge again and I would end up with 6 decent size splits with just 2 cycles of the cyl. If the big quarters are to big for just one extra pass thru the single wedge, raise the 4way and make the quarter into 4 pieces repeat on the next quarter split and you now have 10 pieces of wood with just 3 cycles of the cyl. You just cant do that with a vertical splitter with a single wedge or a non adjustable 4way wedge. Maybe you can, but it means man handling the round to get them in position.
Lifting large rounds using your back, just isnt something I look forward to. You know anything you cant lift by hand is most likely going to need resplitting. With a horizonal splitter, this means at least half of your round is going to fall back on the ground when its split. This means lifting the same piece of wood multiple times to process the one piece of firewood. A table at the end of the beam can catch a lot of wood and reduce a whole lot of bending over and lifting. A log lift can make lifting the logs to the splitter a lot easier than hand loading. A boom with winch can reduce a lot of bending and rolling large rounds to put them on a lift. I like the boom and winch on my setup, but I know it can be improvedby adding a table to catch the splits. Probably a lot of other things I could do as well if I put my mind to it.