The larger the boat, the more important your trailer's brakes are. In fact, if what you're towing is over a certain weight (which varies by state), brakes are required. There are two types of brakes: surge, which react to a sudden slowing of forward motion, or electric, which work in conjunction with the towing vehicle's brakes. Surge brakes, which are far more common, can sometimes malfunction, denying you the ability to back up the trailer. Electric brakes are more sensitive to saltwater contamination. Think about how much time your trailer will spend in or near a saltwater environment. If it's a lot, go for surge breaks, if it's not, consider electric, but make sure the junction boxes are encased in resin to keep out the damp.