The only thing I remember hearing off the top of my head is that the Fast Pack version of VF-11B have addressed the joint problems the originals had. Yamato dealt with weak joints by beefing them up a bit. I suppose you can say they had hip replacements. I guess there have been issues with tranformation problems between the different modes that the new versions no longer have.
Also the color of the Fast Pack versions are slightly different than the originals. Not to say this is a bad thing, just a different shade. But you already know that.
I am not a major collector so I really can't be of much help. I have original Macross stuff like the Bandai 1:55 scale VF-1J. As for Macross Plus, I just remember hearing that the joint issues people were having has been fixed with the Fast Pack.