Paul’s Fishing Kites have conducted extensive research on fish hook types, catch rates by hook type and fishing hook sizes.
In addition their research measured the effects of using a snell knot to attach the fish hook to the line versus tying fishing hooks in the New Zealand snapper fishery.
It was found that the type of fishing hook knots used has a significant effect on catch rates and the snell knot performs best.
Results of hook comparison research
Circle hooks with a snell knot (the strongest fishing hook knots) were found to have the highest catch rate by a considerable margin.
They also caught more than twice as many fish as either O’Shaugnessy and Octopus patterned hooks of the same size.
The method of tying fishing hooks was also investigated and a difference in catch rate between tying a circle hook versus snelling a circle hook was determined to be around 20% in favor of the snell knot.
See the diagrams below on fishing hook knot tying.
Why would you ever use another hook or attachment method?
http://www.fishingkites.co.nz/fishingknots/snell_fishing_knots.html