I use large bark chunk in a wooden basket. In Florida and in my particular area, we experience long periods of hot and dry. Like Arizona at times. I think the extra medium holds just enough water.
But yes, vandas do not like pots unless they are spartan with medium. I have a few, but I let and encourage the to grow out of the pots.
Charles, sure wish we could grow Vandas up here, I've only seen a few in green houses where they seem to be on permerment display! I just wanted to mention that your avatar is beautiful!
Al