I don't have the recent experience to comment on how dry wood splits compared to wet in terms of how easily the wood pops apart, but green of any kind has a tendency to get stringy from my experience. That means you may have to pull apart split pieces by hand, and in larger rounds it can be a pain because the whole round resists splitting more, and if it does split, it can take extra work to separate the halves. Strings in most varieties other than oak want to split in a zigzag pattern increasing splitting resistance.
I find that dry wood seems to be less flexible, so it doesn't let the splitting ax stick in like green wood. I also find that letting the cut rounds dry sufficiently forms splits that only need a little help to go all the way through without leaving strings, good for hickory and even elm. The ease of splitting on the cracks formed by drying can be increased by fungus getting in there. I just split some oak, still quite wet, but dry enough to have cracks. It popped apart even easier because fungus got in the cracks. The trees were cut this spring, so the fungus didn't do any damage other than grow in the cracks.
