I am sure these are all different between them in more than one way, but definitely the most interesting will be the multitimbral VSTs.
That's why, I believe the sorts of Kontakt, HalionSonic or Sampletank will be most interesting.
IK's Sampletank 3 is going to be announced in January at NAMM, and it seems there are a lot of improvements and the interest builds up nicely.
Maybe vArranger could be a best match for such a virtual sound module! That will be killer.