Based on performance, they both do the job. I have had both and I really like the trunnion style the best. Not a fan of the entire round bar set up. That is my opinion of course. See article I found on eTrailer.com
Which Weight Distribution Style is Better, Trunnion Bar or Round Bar Question: which system is better ... trunnion or round/flat bar? asked by: Samuel D
Expert Reply: You will hear arguments for both, the general consensus around etrailer.com is that trunnion systems are the better design. The bars are very easy to remove and install in the head. Since there is no bend in them, they are considered stronger and more durable. Since the head does not come down and the bars do not stick out of the bottom, there are less ground clearance issues. Some people argue that round bar systems are easier to adjust, but you set the brackets and head once and as long as you are towing the same trailer, you usually do not have to adjust them again.
The top of the line system we offer is the Reese Strait-Line Weight Distribution System with Trunnion Bars like part # RP66074. The trunnion bars are typically easier to install and remove from the head and the Dual Cam sway control system that comes in the Strait-Line system is the top of the line sway control that Reese offers. It is a pro-active system that works to prevent sway before it even starts.
If you are pulling a boat trailer with surge brakes, you would not be able to use a system with Dual Cam sway control. Chain attached systems prevent trailer momentum from activating the surge coupler, so you would need to use a friction system like the # RP66153 kit that you were looking at.
If you write back with the gross weight and tongue weight of your trailer, I can recommend some specific kits for you. expert reply by: Patrick B
2015 Eagle HT 29.5BHDS
2014 Ram 2500 SLT Quad Cab 5.7 Hemi