It depends on many factors. Size of the water, forage in the system, other game fish in the systerm, anglers needs/wants, ect. They are currently experimenting with stocking yearlings instead of fingerlings in 3 or 4 lakes in pa (all western lakes). Many lakes get tigers because they grow faster than pures, and they are easier to raise. My vote would be to stock only pures and stock them as yearlings.
All the things said are factors for sure, I believe PA pioneered breakthoughs with the hybrids and dry feeds, so that makes them a bit better from a culture/numbers standpoint..... plus what Ed said about being able to control the population if needed.
As for survival, based on what I've seen (not scientific)it seems that the pures have better survival rates. They are typically stocked at a much lower density too.
As a fisherman I also prefer pures to be stocked since they have a chance at reproducing in the event something happens to the stocking. I do love catching the tigers though cuz they are very pretty. They seem to do better in the waters with weeds from what I've seen. A few reservoirs that I know had tons of tigers stocked & that do not have significant weeds seem to have very few adult fish. There are exceptions though!