I've never had pine that was hard to split, but I don't split a lot of that. I do split a lot of oak, hickory, elm, ash, maple, walnut, etc. I have a 22 ton SpeeCo splitter and wouldn't get anything bigger if doing it again. I've only had one twisted elm that stalled out my 22 ton.
It refused to split any of the logs from that tree as the grain was damp and stringy, and relied on the wedge to shear through the logs. When I got to the logs over 16 or 20" it would run out of steam. We noodled those large logs in half very easily and then it split the halves like butter. That was a lesson learned for future large logs that are somewhat difficult, because even with noodling first, it was fast to get through them. Large logs are rare for me, so I like the swift cycle rate and smaller more efficient engine on the 22.