It's all a big circle on what works for each individual. Hand splitting also good for baseball, hockey, tennis, lax players and gym rats.
I think the key variable missing in my operation is "moderation". If I were splitting 3 - 4 cords per year, like any normal sane homeowner, I'd likely still be doing it by hand. It's much more pleasurable to breath fresh air and listen to the birds, while whacking wood with a splitting axe, than wearing ear plugs and breathing exhaust while humping rounds onto a splitter.
Now, if we want to get back to the question of "time to split a cord", we can't ignore the factor of splitter speed. A few above have already posted on kinetic splitters, but other than my one mention of the fast-cycle Iron and Oak, I didn't see anyone mention fast hydraulic splitters. So, let me give my quick opinion on it.
As already mentioned, the kinetic splitters cannot be beat for speed, if you have a lot of straight and easy splitting wood. Of course, as others above have already argued, and I'd agree with them to some extent, you might consider just sticking with hand splitting for your straight wood. There are plenty of videos on youtube, and even one or two by one of our espresso-loving regulars, showing just how fast you can split straight clean rounds by hand.
Hydraulics, on the other hand, will go thru absolutely anything. I think it's Jags or Highbeam, who love to post a photo of one experience thy had with some particularly gnarly elm. But most affordable hydraulic splitters are painfully slow, like worse than molasses in January slow. Plenty of folks are happy enough to work slow and easy, especially the retired among us, but it's not for everyone. Certainly not for me.
This brings up the third option: fast-cycle hydraulics. Whereas most hydraulic splitters have cycle times listed around 11-12 seconds, numbers that are actually a bit optimistic if you ever take the opportunity to time them on your own (I have), there are some hydraulic splitters that have full cycle times as short as 6 seconds. This is typically achieved by a combination of increased pump and decreased cylinder sizing, for a given HP engine.
Most common among these is the Iron and Oak fast-cycle 19 ton (later re-badged 20 ton, then discontinued) machine, with it's little 3.5" cylinder and 16 GPM pump. I rented one of these several years in a row, and later found my own Huskee 22-ton (11 GPM / 4" cyl) so painfully slow by comparison, that I ended up hot-rodding my own splitter for better cycle time. Now I'm getting the same cycle time as the old I/O "fast cycle", but with a 4" cylinder that doesn't get stuck in the gnarly stuff that caused the 3.5" I/O to fail, albeit with a larger engine, more noise, and (probably) more fuel consumption.
