Spoiler Alert: I got my best results with the rock wool with only 1-2 failures in an entire tray, only decent results with coconut (around 66% sprouted in 2 weeks time, and very poor results starting seeds in peat pots (33% sprouted). Since this was my first time and I know I made at least one mistake each handling the coconut and peat, pilot error is suspected. In any case, this shop has been a good find.