As a former rescue climber I would recommend any system that you can 'precisely' adjust the amount of friction that controls the 'pay-out' of the control line ... and not have to depend on the variable friction under varying wet/load conditions --- usually needing a human brain. That would in my mind more favor the Scott or the Fleming.
Id avoid a "figure-8' for any 'large' area mainsail as 1. you will have difficulty in putting 'enough wraps' on the the '8". 2. if you do get an overwrap with 'multiple' wraps its going to be a major job to get it to 'release'. 3 'strength' vs. a full loaded large mainsail is probably going to be a 'minimum'. The 'figure-8' would be 'worse' for over-wraps; the rescue-8 has 'ears' to lessen the potential of 'overwraps': Rescue 8 : Rock Climbing Gear : Rockclimbing.com
Of course any of the friction type 'brakes' are infinitely better than a rigid 'preventer' which do not allow for any 'impact' from an out of control boom or for a boom that gets 'dipped' into the water.
FWIW - I use the Wichard 'ladder type' on a ~450 sq. ft. mainsail, but find that it needs constant adjustment to get the 'right amount' of 'slip'. The Wichard supplied 'rope' is VERY stiff (kernmantel?) and is quite hard to set up precise friction.