Although the preponderance of evidence seems to be in favor of the habitat selection hypothesis, some evidence for natal philopatry has been observed in cuckoos and the majority of cuckoo eggs are found in nests and among eggs matching their foster species, which supports the nest site choice hypothesis, but does not invalidate any of the other hypotheses. It could also be the case that there is more than one mechanism of host selection at play here.
Although the majority of evidence appears to support the habitat selection hypothesis, some evidence suggests natal philopatry in cuckoos, and most cuckoo eggs are found in nests and among eggs matching their foster species, which supports the nest site choice hypothesis but does not rule out other hypotheses. It's possible that multiple mechanisms for host selection are at play.