Well, here we go!
I take exception to the traditional vertical machines. I have a bad back (L5/S1 partially removed), and to sit there and have to lean forward to position rounds, and remove splits, would do me in faster than the cycle time!
Now, with that said however if you look at some of the purpose-built Vertical Only machines like the "Super Axe" from Australia, and some of the other custom built (USA) machines that have a table height about waist high, with a log lift, that's a different story: These machines make a good arguement for going vertical. It seems that high expense is the issue here, unless you custom make your own version.
Ultimately, I still favor the horizontal models, and in another thread:
https://www.hearth.com/talk/threads/61527/
I have begun a nice exchange on building your own horizontal machine.
I beleive that if you study all the options available with a horizontal machine, you can have your cake and eat it to! Working height can be "Lumbar Friendly", and if the design is planned out carefully, you can have the machine pushing the splits right where you want them: into the back of your truck? Sure! In a pile next to where you will stack them - Yup! AND, all with no heavy lifting either!
Log lifts can be accomplished with hydraulics, or in a more cost effective manner with an electric linear actuator, a winch or a winch/truck lift combination. I may opt for the winch/truck lift in addition to a hydraulic log lift, because the winch/truck lift can be used to drag heavy rounds to the splitter with its' 30 foot cable, and could even be used to lift/position those logs you have not bucked yet.
The lift I'm talking about is one like this, that would be mounted at the cylinder anchor end of the beam:
http://www.harborfreight.com/1-2-half-ton-capacity-pickup-truck-crane-with-cable-winch-37555.html
The other thing to think about with the machines that are H/V (Horizontal/Vertical) combos, is that the splitting wedge is on the ram, and not at the end of the beam. This causes some concern, as the splits fall to the sides, and without side tables can land on your foot if you are not careful. Having the wedge at the end of the beam (and therefore just a push-block on the ram) allows the splits to be driven off the end of the beam, and if you have a tray/table at the end of the beam it will not only catch the splits, so they can be re-split to a smaller size if necessary, without having to pick them up off the ground (no bending over), but it allows the splitting action of the currently split round to push the splits on the table right off the end of the machine into your truck/bin or whatever, nicely out of your way. Some folks let the pile build up, and then allow the splits to use reverse action to push the machine away from the pile as you continue. I can't say I've ever done this yet myself, but it sounds like it might actually work.
Yes, the nice vertical machines are great, but to accomplish the same type of action I just mentioned with one, it would require the addition of a conveyer/elevator, which while they are kind of cool and VERY convenient, they get VERY pricey, even if you could make one yourself, and it becomes just one more piece to lug around and store. The one shown as an optional add-on to the Austrailian "Super Axe" is very well thought out and quite a nice piece, but I'd guess way out of the affordability range for most.
If you are handy, can lay a decent bead (weld), and can do some light fabrication work, it's quite surprising as to how nice of a machine you can build if you carefully think things through and take your time. I've been borrowing splitters (which gives you a good idea as to the benefits/limitations of various designs) and in the mean time I've been researching and planning out my splitter. If I were going to purchase a commercially available splitter it would be from either Timberwolf or American CLS. In my opinion these are the two best US built machines available. The problem for me is cost. I'd have to easily spend a minimum of $3000 - 3500.00, to get a machine similar to what I'm planning to build, for considerable less money. Of course I'm not including my labor costs, but that's a given, and how I can have a better machine for a lower price.
I have my cylinder, valve, engine, and some other misc parts. I have to buy my I-beam and some steel, etc., and will soon have the sparks flying as I begin assembling my "Frankenstein Splitter".
Take your time, talk to lot of folks, and enjoy the journey. To me a large part of the fun is in building it myself and then having the satisfaction of using the machine I built to get my splits ready to stack, season and ultimately enjoy as they warm my weary bones! ;-)