100% by hand. there was a splitter here my boss made (it is as old as me in years actually), then delivered after he upgraded the engine to some expensive kohler unit. That broke at around 20 hours, plus the hydraulics broke as well, started leaking all over. I hauled it off and stuck it by his shed. I never asked for it in the first place, always enjoyed hand splitting. About the only thing I liked with the hydraulic is the log lifter for those 300 lb mambo chunks..
There's a thought, not a full splitter, but just a powered lifter for hand splitting big stuff.....hmmmmm
The bulk of my wood is done with the fiskars now, sometimes I have to use a BFH and a wedge, but since I got the hang of effective fiskars use, that rarely happens anymore. From 6" to over 30", most any species now. Some I do green, some semi dry, some I leave until the rounds are real dry and fully cracked, just depends.
I have enough wood I don't fool with it, if it doesn't show signs of splitting easy, I throw it back on the "to be tried again pile" and I let them dry more. Eventually they all split.
I take the harder to split stuff as a challenge, try to figure out a diff technique for them, adjust my swing and angles, etc. Most stuff splits easy though, or "easy enough".
It's faster too, for most wood. If you had a splitter that cycled as fast as I can swing and reswing, that would be one freeking dangerous splitter.
Hand splitting is half and half, reading the wood is as important as your tool selection and use (speed and aiming).
If I was doing commercial quantities, 100s of cords a year, sure, some powered splitter or processor unit with the multiple wedges, but I am not at this time, so hand splitting it is.