I'm with AA, as had bad service from RAC, more specifically it's contractor KERLEY's of Norwich.
They recovered a car for me from Norfolk to Erith in Kent, as new auto box packed up after 15 miles, in the process they managed to gouge badly all 4 wheels, which were 15 miles old, I refused to sign the form until I had put this down on it, RAC still refused to pay for them, even though only fitted that morning by mot place as new in perfect condition.
1 other time my dad used them was when his rover sd1 broke it's fuel pump, in tank on these, they sent three vans to fix the problem(one at a time) despite being told it was the pump, then a breakdown truck from 80 miles away to recover home(5 miles away).
The other reason I use AA and not RAC is because rac will not recover cars after an accident(according to policy) but AA do.
The actual mechanics are all pretty good, with nothing to choose between them imo.
tabetha