Over the last 6 years or so I have followed and experimented with many different soil mediums. I have seen and critically thought about all the arguments and data that has been put forward here in Australia and abroad.
Personally even though we are only beginners, as far as documenting this I think Ken and myself have been at the fore front of sourcing and trying new mediums.
There are so many variables when it comes to analyzing mediums that anyone stating that a medium does not work because >>>>> sends alarm bells ringing.
Trees will grow well in any medium, it depends less on climate and more on technique, care habits and sifting.
A medium such as diatomite and zeolite will never hold too much water in any climate. In fact any medium graded to a reasonable size particle will never hold too much water as the air will circulate around the particles.
Even a medium that breaks down faster than others will usually last long enough for the roots to colonize and create structure. Unless the tree is in poor health.
This is one of the main factors in medium discrepancy. Any medium will only drain so much. Then it will be up to the tree to use up the water that left. If the tree is not healthy it will not take up much water and the medium will stay wet MUCH longer.
The best thing you can purchase to improve your medium is a sifter
Edit: one thing I have missed in this is that a certain medium may need extra care in fertilisation or such. Not accounting for this could lower the health of the tree in the medium and hence use less water and cause the medium to stay wetter longer. I still classify this in care habits although it directly relates to the medium you are using.
It's too bad your in such a hurry cause the stories I could tell you, Bushels and baskets of stories, hole crates full of stories. But if you can spare a moment I will tell you one story.
Most comments from people I hear re diatomite is that it cannot hold Moisture so must be no good 
