Well, Seedfork, I haven't been paying real close attention. Within the same pod, though, I expect seeds will react differently. I had 8 seeds from a cross of Purple Many Faces X Lillian's Vapor Trail that I planted on 8/18/14 the day the pod cracked. On the fourth day after planting a seedling was up, but it took 'til today for the next one. I've just noticed that those planted the same day have had seeds that sprouted fast, but not every seed in the pod. It may just mean a longer time between first and last within a pod. If you have to wait for the last one, it may not be a benefit at all. If you want them in a hurry and are willing to sacrifice the later germinating seeds, then it might be a good thing. But not any trials or comparisons on those that waited. Because I had a lot of pods with either the same pollen parent or a pollen parent I didn't keep up with, I tended to store my pods in a checkbook box in the fridge until I got the last one. I was running out of containers, you see
. So when I did that and had quick germination, I couldn't say for sure it came from the fresh pod.
As for the different seed starting mediums. I don't think any potting soil is an ideal seed starting medium. It's too coarse, it has additives and, IMO, has too much clay content. So it both retains moisture too much rather than draining and it sets up hard like a brick. The additives may or may not be detrimental, but the gummy, coarse texture isn't ideal. It's all I had on hand when the pods started to mature, so it's what I used. I need to read what actually in the other bag, but it really does look like Canadian peat moss ground to nearly the texture of cornmeal. So it's light and doesn't gum up, but it does dry out pretty fast.
I hope this is helpful, because I'm sure not any kind of expert on growing daylilies from seed. I haven't done before. No way could I even be called a knowledgeable grower of dayliles, for that matter. They were just on my bucket list to grow successfully. Over many years I've grown many things with good success, but daylilies weren't one of them. When I finally had some success, the drought set in and the deer thought they were a banquet just for them. So after a few years rest, I'm trying a different approach to growing them. Fun this year, but no guarantee for the future.