This is an interesting question. I believe in the float and slowly add water over time method for fish, ( adjusting pH and salinity and others ) but what about corals?
When your Retailer, wholesaler, shipper, MO store get in 25 - 100+ pieces at a time, do you think they are spending an hour with each acclimating them? I don't think it is likely. (I have seen it in action at many levels) Many just float for a few minutes to acclimate temp and then do a coral dip and drop it in. This can happen several times to each peice as it goes through the channels of shippers. Of course many will say that all of these parties are planning on keeping the animal only a short period of time. But if there is continuos dieoff, that party won't be in business long.
That being said, I have been keeping reefs for over 20 years and salt for 30. A few years ago I started experimenting with my new corals. (LFS only, I have just ordered my first MO corals, more on that in another post) I would buy similar species from the same store, at the same time and acclimate one the "long" way and one the "quick" way in the same tank. Place them in similar areas of the tank and wait and see.
I have only done this about 15 times, so it is hardly the kind of numbers we will see at an LFS, but I have had only 1 death of the 15 or so corals "quick" dipped. That's a 93.3% success ratio. Not bad....