Reading the advice above i think i only have some small additional information.
In general i find that there are 2 mayor factors for deciding on potting medium.
1 is root thickness. The thinner the roots the finer the medium
2nd is the relative humidity. The dryer your condition the more water retentive medium like perlite, sphagnum you will want to use.
All of this is depending on your watering tendency's. As long as you adapt your watering regime to the needs of the plant, almost everything would be OK.
When you want the medium to adapt to a specific regime you would like to apply (water 1X a week for example) you will need to experiment with medium size and content so it will suit your growing conditions and habits.