Not to run against the grain here, but,,,,,
Obviously from a "get it dried as soon as possible" standpoint, splitting it right away is the best policy. However the OP could have years worth of wood already hoarded away and is not worried about getting this wood dried in a big hurry, and just trying to make his splitting job a little easier by finding out if letting the rounds sit for a while will help. Certainly from an "ease of splitting" standpoint, sometimes bucking the wood and letting the ends check and split a bit will facilitates how easily the rounds will split. This can be especially true when hand splitting hard to split varieties of wood. It is definitely true of Lodgepole pine, and Douglas fir I have cut and let sit in the hot summer sun for a week or two, but I don't think letting it sit for a week or two in the winter would help much at all.
The other thing to consider is that some varieties of wood are easiest to split while green and get harder as they dry a bit. That wood in the pictures doesn't look like douglas fir, so it must be some other type of fir that I'm not familiar with, so I have no idea if letting the rounds dry a bit will help make it easier to split.
Warmguy, you may have to do your own experimenting. Split some now, and leave some rounds for a while and let the ends check and see if they are any easier to split. But remember, if you are thinking to burn it next winter you better get it all split ASAP.
