Voted Paignton due to their many strengths in this category: species large and small that are native and endemic to tropical rainforest / forests, species from across biogeographic regions that comprise the tropics, species across all classes whether birds, reptile, amphibian and mammals.
Dublin / Fota by contrast seem to me to be an uninspired collection that focuses on larger ABC mammals many of which are held by zoos the world over.
The conservation output of Paignton is truly enormous when you consider the Whitley conservation trust and the way it supports and funds conservation initiatives / projects the world over year after year. This is particularly the case with funding in-situ conservation within tropical rainforest biodiversity hotspots.
Dublin / Fota by contast do not have that large a conservation output though they do financially support in-situ projects with rainforest species in Africa and the Neotropics like the golden lion tamarin, lowland tapir, okapi, bongo, orangutang, gorilla, chimpanzee, siamang.