I also was unaware that Associated ever used anything Castle in there RTR RC cars. I have always seen them use Reedy and other systems owned by the company. From what i have tried and seen i was never a big fan of the systems Associated included with there RTR RC's.
The best systems i have seen in RTR RC's has always been the Mamaba systems. IMO they are some of the best brushless esc/motors out there and have no problem buying them for kits i have built in the past with amazing results. I also have never had there ESC or motors burn out on me like some other brands.
I dont think it is fair to compare Hobbywing to Castle. Castle systems are of much more superior quality and the motors offer much better powerbands. The powerbands in the Hobbywings i have tried were not good at all and some of them seemed to have no power early on in the rev and then when you got to the end of the rev, the power would kick in a little but nothing compared to the Mamaba motors.
IMO, for the money Mamba motors are hard to beat. They kick ass!!!