Prime Matter vs. Haecceities

As I explained in an earlier post, the use of prime matter as a way of grounding numerical distinctions between substances in the same infima species results in an attractive form of "moderate realism," with a powerful explanation both for specific sameness and for intra-specific plurality. There is, however, an obvious alternative: the use of Duns Scotus's haecceities, which are properties of primitive thisness. On Scotus's picture, what individuates Socrates and Plato is not their respective prime matters but two special properties, one of Socrateity and another of Platonity, properties that, as a matter of metaphysical necessity, can only be instantiated by Socrates and by Plato (respectively), and which Socrates and Plato instantiate whenever they exist.
 
Is there any way to evaluate the two proposals? I think there is: we have to look at the problem, not only of individuating whole substances, but also of individuating all of the quantitative or material parts (both actual and potential) of substances. Consider, for example, a perfectly symmetrical starfish. Each sector (one-fifth) of the starfish is (let's suppose) qualitatively and functionally interchangeable with the other four sectors. The sectors are conspecific as parts of the whole. Thus, we must individuate them --find something that can ground their mutual distinction. For Thomists, this is no problem. The prime matter that individuates the whole starfish is infinitely divisible: it contains five non-overlapping parts that can also individuate the five sectors from one another. There is no redundancy involved: the same thing that (as a whole) individuates the whole starfish from other starfish in the same species also individuates (as the sum of five parts) the five sectors from each other.
 
Scotists will have to posit haecceities, not only for the whole starfish, but also for each of the five sectors (with six haecceities in total). Consider a perfectly homogeneous bronze sphere. We will need haecceities for every part of the sphere--for every hemisphere that it contains, for example. Thus, we will need an infinite number of different haecceities for each such sphere (assuming the continuity of matter).
 
So far, this seems like a tie. Both Thomists and Scotists require an infinite number of individuators. In fact both require the same infinite cardinality, probably aleph-one, the number of connected, smoothly-bounded spatial regions. There is, however, a crucial difference. The Scotist account involves an infinite number of redundancies that are avoided entirely by the Thomist account. Consider again our starfish. Once we have the five haecceities for the five sectors, the sixth haecceity (for the whole) is entirely superfluous. The five sector-haecceities suffice to individuate the whole starfish from all other starfish. In contrast, the Thomists have just one thing (the whole mass of prime matter) that simultaneously individuates the five sectors from each other and the whole starfish from other starfish.
 
To match the elegance of the Thomist approach, the Scotist would have to posit that each haecceity is composed of an infinite number of "smaller" haecceities, each corresponding to a proper part of the whole. However, it is far from clear that properties can be composed in this way. And, if we suppose that they can, then the whole difference between haecceities and prime matter seems to disappear. The difference threatens to be merely verbal.