Advantages of the Redarc over the Tekonsha - more versatile installation IE the electronics can be at any attitude and remote to the user control

Advantages of the Tekonsha over the Redarc - better (much better IMHO) manual sway control or overide, simpler user interface and easily swapped from vehicle to vehicle as Tekonsha sell the wiring and cradle seperately if req'd.

Al-Ko ESC - isn't a true ESC in the full meaning of the term so, IMHO, the manuf is using a bit of advertising spin there. Basically it is an automatic version of the Tekonsha manual override.

Dexter - best of the bunch for anti sway as it is closest of the lot to a true ESC in that it uses yaw sensing and differential braking. Therefore, the trailer will track inside the vehicle path and not pull the arse end about as much as the Al-Ko or Tekonsha method.
Fairly expensive and complex tho.

Well, that is my understanding of it all at least...