Since the silicon escapement parts are a key difference between the standard Zenith Tipo 2 ("Cairelli reedition") chronograph and the PuristS' P15 edition, I would think that the distinguished circle of puristS assembled here is well aware of the advantages of this material. Otherwise, we would not have a forum dedicated to Ulysse Nardin, the pioneer of the silicon escapement.
Other than that, I would personally not include the Calatrave in the list of a definitive collection. The Calatrava is too much an entrance level Patek, and as such compromised in terms of finishing quality. If putting aside the money to sav e for a "real" Patek is not an option, I would rather decide an at least equally fine watch from a manufacturer without such a "big" name.
Marcus