Picked Calypso, so much easier to cycle your loots in AH in a day or two to get back out hunting, Arkadia takes week or two for sales to get picked up and usually at much lower MU for most stuff, in my personal experience.
I think it is completely due to player base being larger on Calypso so there are more people willing to bite on markups where you rely on on a few people on lower populated planets to pick stuff up for any markups.
I occasionally go to Arkadia to hunt and try to sell there but eventually 90% or more of my looted stuff finds it's way back to Calypso to get sold because I get tired of paying AH fee's or standing for days shouting to not sell anything. Just no demand for most of the loot on Arkadia, because no big demand for alot of crafting because all the big crafters ground out all the unique bp's so no need to craft non-stop. I believe weapons got so eco and to many items drop in loot to make crafting going on a regular basis, so most mats are not worth buying constantly. About only time non calypso planets get lots of loot sells is when they add new bp's for the big crafters to got there and try to gather them all up as fast as they can, which causes them to go on a buying spree of mats.
The only reason Calypso seems to have constant sales is because pure amount of people here and a lot of gambling crafters compared to other planets. No matter what it will be hard to get most people to change planets for any length of time because Calypso just seems to always be the trading hub, for all planet materials. Heck I bring other planet stuff to Calypso and it sells faster then Calypso stuff. But dealing with stupid space keeps me mostly grounded on Calypso, hunting on Calypso, with an occasional outing on another planet.
Just my opinion on the matter.