I’ve seen and read some posts about this before and for the life of me I can’t find them now when I search for them. I just want to make sure which one would be better before I remove my seeds from stratification.
I have tried both and prefer the cell trays for my more prized seeds. I put a few seeds in each cell. For OP or less interesting crosses, I will use the open trays. If they are in their own little plug, you can let them grow on a bit more without worrying about the roots getting tangled up.
When I was more actively hybridizing I would germinate my seeds in small ziplock type baggies, sometimes upwards of 50 seeds of same cross to a bag, then, if and when they germinated, I would generally prick them out and pot them into recycled annual six-pack tray types, 3 or 4 of same cross to one cell, on the assumption that most would be quickly culled.
I like keeping un-germinated seeds in stratifying bags to save space and to prevent late germinations from bedeviling me and my tracking.
Would be interested to learn of more efficient approaches.