I also vote for surge brakes but there were a few things about
electric that were incorrect or at least misleading.

I have a travel trailer with electric brakes.
They do work in reverse.
In fact they work so well in reverse that I have to turn them
off when backing as it becomes very difficult to back into my
home parking spot with them on.

Some electric controllers use a pendulum and they may not
work in reverse.
Other controllers simply are tapped into your brake lights.
When your brake lights are on the controller is applying braking
voltage to the trailer.
Since every car or truck I've ever seen has brake lights that work in reverse,
this type controller would also work in reverse.

With most any controller it is a simple thumb wheel adjustment to
change the sensitivity of the electric braking. The adjustment
on surge brakes is not at your fingertips.
If you remember to do it, it's a simple thing to turn them off
when you have launched your boat so as not to skid your tires
when you are parking the empty trailer.
Don't forget to turn them back on when you put your boat back on!!

I still vote for surge but electric have moved up in my opinion from
years ago.

Peace!
Dan D. Louisville Ky good ole USA