The first two sources are from the 1995 report that is also referred to by Practical Sailor. At that time, the Trilens reflector did not exist.
The other two are from the Ouzo accident investigation in 2007. The conclusion is that none of the passive reflectors can achieve the 10m^2 criterion. The large Trilens has the second best RCS of all passive reflectors, after the Polaref whose price-point (2000.- British pounds) gives some pause. Predictibly, RCS of the the smaller Trilens is considerably lower but it still outperforms all passive reflectors except the large Trilens and the Polarref for healing angles exceeding 15degrees (which of course is of great interest for sailling vessels). As a side note, the Davis is the worst of the octahedrals.
I agree with your conclusion that active radar plus AIS is best. If this is not in the cards, and neither is a $4000.- passive reflector, then these reports, in agreement with the Practical Sailor study that I cited, all agree that the Trilens is the best solution.