Oz,
Wrong, not "just because of the datalink".
As an ADS-B, the UAT (or VDL-4) has exactly the same ATC utility as 1090ES, and both the forgoing do NOT have the limitations of 1090ES, already becoming evident (as clearly forecast by FAA/Mitre Corp.many tears ago -- at least 15).
As I know, and I think you know, no major supplier has offered a TCAS 11 using the long available standard for incorporating ADS-B IN --- because it provides no additional functionality over TCAS 11 without ADS-B. Put another way, why pay money for nothing.
Your preferred position is and always has been no form of surveillance for GA PVT VFR!
Correct (in other than Class B and up airspace) because there is absolutely no cost /benefit justification for such surveillance, in air safety or any other terms.
1090ES operates outside ground station coverage in real time with SSR and TCAS
An interesting statement, the first part is only true if there is somewhere where there is SSR coverage but no ADS-B coverage, the second is only a TCAS11 transponder function, nothing to do with ADS-B --- because the ADS-B capability is not being used for TCAS 11 -- see above.
As we now clearly know, ICAO and FAA got it right in the first place, and the "quick, cheap and easy" 1090ES "solution" that was the late entry by the major electronics manufacturers (who didn't control any of the UAT/VDL patents) and cash strapped airlines at the time, who were gullible enough to believe the claims of the capital cost advantages of 1090ES, is costing big time, compared with a cost of a stand alone UAT system --- which brought with it a broadband data link, which airlines have now had to fund and fit anyway, as a separate item
Effectively, airlines have been faced with all the costs of fitting 1090ES AND the equivalent of UAT.
What a great win ???
Tootle pip!!