I've gone through a few different servos in my short time with 1/8th scale buggies. And I've tried a servo with right around 100 oz/in torque and found this to be acceptable for bashing but not that great for racing. I 've also tried the old trust Hitec HG 645mg and with it's 133 oz/in of torque it was better but didn't find it fast enough for racing, I'm currently using an ACE/AE 1015 servo for both steering and Brake and they are great. But I'm sure there's going to be guys after me talking about the new High Voltage servos with a outrageous 425 oz/in of torque to be their babies. I would suggest any servo over 170oz/in of torque and speed is really your preference. Some guys like really fast servos some like fairly fast. The guys that don't like really fast servos say they just don't drive smooth if they are too fast so they use the slowness to help limit twitchy driving.

Good luck with your choice.