I'd say go for three in one. See what the outcome brings you. Why change what you've already started? Learning is about going with your intuition.3seedlings in 1 Dixie cup
I would sooner use an old paper coffee cup than put 3 in one Dixie cup....but what do we know, it may yield a poundthe only reason to do this is that you cant afford more Dixie cup or soil but I still wouldn't do it