I'm no expert on uncased cakes but I'm thinking that pretty much any of the mentioned substrates will do quite well. I am guessing that most people will say that the one they use is "the ultimate" one, especially if they use birdseed. 
Seriously though, I don't think anyone has really done an experiment comparing the yield of cased/uncased cakes based on different substrates. There are so many variables involved it would require a truly scientific experiment, one that most people with homemade terrariums would be unable to conduct. I wish you future success however and don't be afraid to experiment. I would suggest however that you start small if you do, I just lost 10 jars and a spore syringe due to a mistake in new substrate preparation, blah.
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-snarf