Das,
Have to agree with Ed on this one...
But I did notice you have in your post:
Eventually do a Scale Project
Given that part I would say go with the Twinstar
as it is about the highest wing loading of the three..
The Dual Ace flys slightly light,, both are very
predictable..
Nowww, the CH Twin Stix,, what can I say..
It is just plain ole fun no matter how you look at it..
But as a twin trainer,, hhmm,, I would have to say no..