I've spent years running the protek 160T servo in almost all my 10th scale vehicles. Recently, a friend mentioned trying the 140t. A hair slower and when you turn the 160T down too far it get's notchy. The 140 has a better feel for some. I bought one to try, but it has the torque, it's low profile and it's plenty fast. I'll still need to turn it down a little I'm sure.
I look for 175 oz of torque, replaceable gears and a 1 year or better warranty. I have some MKS I really like too, but they are all too fast.