I just found this report. I think it speaks volumes
Rainbow trout Mortality Flies 6-11% Bait 25-64%.
Source: Hooking Mortality - a review for recreational fisheries 1994. Reviews in Fisheries Science. 2(2):123-156.

I don't know anything about this review but the numbers seem to be what some people are going to look for. I doubt that we will ever see a report done on Teimco 7999 (steelhead fly hook) and Gami's size 2. All hooks are some what different. A size 2 bait vision hook will not be the same as a size 2 bait Gami, will not be the same as a size 2 Diachi fly hook.

JJ