I've been heating solely with wood for 12 years now, about 5 cords a year. Most of my wood comes from a local log processor; I get the butt ends and crotches for free. Most of it is high side of 20", and the big ones go upwards of 40". It's all hardwood, mostly oak. He doesn't bother with pine and neither do I. The biggest I've split was from another source, a 54" round of the hardest ancient oak I have ever seen.
It's all been done with a Tractor Supply (Speeco) 35 ton. I bent the toe plate on a crotch from the same tree that gave me the 54" round. That stuff was HARRRRD. Speeco replaced it under warranty, no questions asked. Other than that, it's been trouble free. Speeco had a run where they skinnied up the toe plate, and replaced a lot of bent ones. They learned their lesson and beefed it up again. Newer owners tell me they have no problem.
I run Rotella T6 in it, and one of these days I'll probably swap out the hydraulic fluid for DexIII/Merc for better flow in winter.
I like the vertical/horizontal option, and I plan to build a log lifter for it this winter.
That said, what you need depends on
you. What will you be splitting? How much? How big? What species? A 22 ton will do you just fine if you are splitting pine and the lighter hardwoods,, or small stuff of just about any species. I've had people tell me they split big oak with their 22 ton and never a problem, but my 35 ton (and the Speeco IS a true 35 ton, unlike most) has been stopped more than once by a big oak crotch.
If you are splitting big stuff, go big. Pay once and cry once. Get a log lift if you work big stuff, unless you have a
grapple for your tractor to handle lifting it.
By the way, most manufacturers lie about their tonnage ratings. They claim xx tons, but that's if you run it at the system's max pressure, and they don't. Max is typically 3500 psi, and they run 2250 or 2500. Speeco gives accurate ratings, they run at 3500 so you get a true tonnage.
I've heard nothing but good about the Iron and Oak, too. FWIW, I bought a few wedges and a maul from them early on in my spitting career, and the maul broke after one season. The wedges were pretty soft and mushroomed badly pretty quickly. That was before I got the splitter and I was doing those big oak rounds by hand.