I have tried most servo's in 1/8 offroad. The best I have found have been the Futaba 9350. Most of the serious racers in my area use the 9350 on at least steering. I use it on both and my new xray just got 2 new ones. I own a total of 8 of them between my trucks and buggys and have used them for the past year witout a single failure. U burn allot of fuel and have really put them to the test. Everyone has their favorite and the 9350 is mine.
For the record most receivers only will put 5volts out to the servos if you plug the battery into the battery slot. I use Jr radio and receiver and they must have a diode in the receiver that will not let you do the trick of plugging the battery into the 3rd channel and pluging your personal transponder into the battery slot so I am stuck with 5volts unless I run a splitter.