Guess I'll bring this thread back to life.
Horizontal splitters are far more efficient and more ergonomic for the user. They also offer more options; 4 way, 6 way wedges, Wedge Lifts, Tables, Conveyors, etc. You really should not put a 4 way wedge on a splitter where the wedge is on the piston. It will try to twist if you hit a knot. Also, horizontal splitters, if you use it in one area, can be modified easy enough for production. A simple I-Beam height table with a ramp and a helper will make splitting fast. Horizontal splitters also have provisions for Log Lifts. When logs are small enough; you can pre load the lift so they just keep rolling into the splitter as you need. The proper towing position for a horizontal splitter would be to have the tong on the engine side so you are splitting away from the hitch. This allows you to keep it hooked to the Tractor, Quad, Truck and just pull forward if the pile gets to large. By doing that in reverse, you have to pull the splitter through the pile or keep moving the pile.
For these reasons Horizontal is best for production. However, most home owners will not need speed and are working it alone so Horizontal/Vertical would make do.
Timberwolf is a superior splitter designed for people who are serious about wood production. It is the Cadillac of splitters! You just have to ask yourself, are you driving a Cadillac? No, they are not for everyone. I see Harbor Freight has a Horizontal with Log Lift for under $1,800! Even though the table is backward (hitch is on the wrong side) you can burn through two of them for the price of one Timberwolf. Timberwolf's design, wedge style and pump quality, make it strong enough that you don't need more tonnage to compensate for design flaws. This is why they don't have huge 30 ton machines until you get much bigger.
Auto Cycle is great, Table Grates are Great. But when it comes down to it, just about any splitter will be easier than an ax! Just about everyone, me included, will always buy more than they really need.
Look for used splitters, there are a lot of them out there! 6months old, 1 year old, home made. A lot of people that buy splitters soon learn they would rather just buy split wood! The shear cost of a splitter $1000+ will go a long way toward buying pre split wood! Unless you are burning enough wood and getting it for free, a splitter doesn't make financial sense for many. Something a lot of buyers don't realize until after they buy it. Thus the reason so many new ones are sold after the first year.
http://www.Craigslist.com is a great place to find used splitters.
Have Fun and Split Safe.