I find that fish are stressed enough from shipping and packaging. Putting them into a sterile system usually lacking the same level of filtration as the main tank seems even more stressful. Good luck!
I see these two 'arguments' all the time. Versus putting said stressed (and probably malnourished) fish into an environment where some percentage (sometimes all) of the residents want to kill it? Done properly, QT is actually much less stressful. Just because a fish dies in QT does not mean QT was the reason. May have died in the DT as well. Correlation is not causation. At the end of the day we all do what we think is best for our system and circumstances. No better source of fish than DD, but I have had velvet once. Good luck to you