I have a 27 ton splitter that does a decent job and I have found some pieces that would stop it. At the time that was what I could afford. I would have rather had a 35 ton model but did not have extra cash. Get the biggest splitter your budget allows.
Isn't most splitters tonnage rating fudged/inflated ? A 4" cylinder with relief set at 2500 lbs. is just under 16 ton push. A 5" cylinder with relief set at 2500 lbs. is just under 25 tons push.
A 4" cylinder will split all but the gnarliest pieces.
Those who say their splitter has split everything they've thrown at it just haven't been splitting tough wood.
Does everyone need 35 tons? Nope. Depends what you're going to be splitting. Most of my wood is large oak, and a lot of it is crotches. I need 35 tons.
If I were splitting mostly straight grained stuff, I'm sure 22 tons would do the job.
I've got a 20ton machine (4"cyl, 11gpm, 13sec cycle) and I only occasionally want more tonnage, but often wish for faster cycle times.