Is there a capability difference between 3D Touch and Force Touch?
This is a lot like asking if there's a difference between a Nissan Leaf and a Maxima. Both are cars, they seat 4 people, and they move around. The technology powering them though, is radically different. Wikipeadia has the 3D Touch redirect to the Force Touch page, which is misleading (and incorrect). This article does a slightly better job explaining it, though it sort of steps on its own tail. Basically, Force Touch reacts based on the actual force (hard, medium, soft) where's de 3D Touch reacts based on the kind of touch (or tap): quick, prolonged, etc. 

EDIT:

On second reading, you ask more about capability than implementation. 3D touch is definitely more sensitive than Force Touch, but with only the 6S just rolling out, we'll need to wait and see what Apple chooses to do with this enhanced capability.