We had a boat that was about 8000lbs combined on the trailer. The trailer had hydraulic drum brakes with a surge actuator coupler. I absolutely hated this setup. I know, comparing a surge actuator and tow vehicle operated brakes is like comparing apples and oranges, but I never felt like the hydraulic drum brakes did much.
About 4 years ago I replaced the drum brakes with Kodiak disc brakes and a disc brake surge actuator. The new setup made a world of difference.
The disc brakes on the boat trailer stopped so much smoother and with more force. They also ran much cooler, never had the bearing grease seep out even after towing through the mountains. With the drum brakes, a drive over the mountain was a nerve wracking event and we had grease seep out on a few occasions when the drums heated up (even with new seals and bearing buddies). I didn't feel the boat trailer pushing the truck with the disc brakes as I did with the drum brakes. As an added advantage for a boat trailer, the disc brakes didn't hold water like the drums did, yes I know most RV's don't have this problem.
I realize that a properly adjusted and controlled set of drum brakes are ample to stop most trailers on the road, they are still the industry standard and probably 90-95% of trailers on the road are using them. However, disc brakes became the standard for automobiles (and trucks) a while back for a reason, they are just better. If possible, our next towable RV will have them when ordered or shortly after bringing them home.
OJ