How, ultimately, would you distinguish between the contact subtypes of two types having the same ego functions? Examples would be LIE-Ni and ILI-Te, LII-Ne and ILE-Ti, and so forth?
I realize one tempting answer is to say "Model A distinguishes them by way of the differing information element positioning within the respectie blocks."
However, I still wonder beyond this, as ultimately the reason there even are 16 types is the model of pairing a rational and irrational in the ego block, so I would consider the rest of the model more of a result of theoretical and empirical weighing based on the goals of socionics theory as to what can be said of the organization of all the other information elements.
The answer "A LII-Ne is ultimately founded on introverted logic whereas ILE-Ti on extraverted intuition" is also not entirely enough to me, because each of these subtypes represents a strengthening of potential in the direction of the creative position (along with certain other strengthenings as a consequence), which means to me that a blatant restatement of the irrational and rational base statuses is not getting at the heart of the issue conceptually without elaboration as to what these statuses mean, particularly in the creative subtype situation (in other words, I realize they are different types, but the point is to theorize what defines these types).
Perhaps a clear distinction between base and creative roles in these kinds of subtypes would be illuminating, or some generalized description of inert/contact functioning that you have found helpful, extrapolating from/building on the basics in a site such as wikisocion, or perhaps even better, if you have a higher source of information on this. Or a description of what strengthening of potential does and does not entail.
I admit I am not confident in my recognition of how dimensionality plays into the model beyond a basic factual knowledge, but that could be a good start, as increased potential towards 3D remains different from 4D.