The others you mentionI don't know but Dehler that had built balsa cored boats for many years is changing. I don't know why but building with balsa is cheaper than building with a high end foam and I am sure it is no better. I know particularly the Dehler 41 where the cheap version has balsa core and normal resins while the expensive version (lighter and stronger) is made with epoxy resins and top foam core.
I have observed that more traditional brands still use balsa and more modern and technical boats use almost all some kind of hi-tech foam and epoxy or vinilester resins. I guess they have a good reason to do that and it is not price for sure