Let's kinda divide the world of servos into 4 basic categories.


Sport off brand
Sport brand name
High performance
Digital




Now, let us agree that your control system is only as good as its weakest link. Repeat in your mind for full effect.


Sport off brand servos are fine for trainers up to .60 sized engines. Resolution, power and speed are not important. Cost is also a factor so they make a good choice. Generally in the 40 to 45 inch/ounce range with a transition time of .20 to 25 second.


Sport Brand Name Servos generally are an improvement in performance and service at a small cost. Generally in the 40 to 45 inch/ounce range with a transition time of .20 to 25 second.


High Performance servos vary a lot, but generally you have a choice of speed with lower torque or torque at a lower speed. I consider a minimum of 70 inch/ounces at .15 second to 120 inch ounces at .22 second with a coreless motor and ball bearing supported output shaft to be high performance. There are a few that have both power and speed such as the Futaba 9402 and are quite expensive.


Digital are better, but not by much. Generally offer the same speed and power, but in specialized situations can provide a slightly tighter feel. Most expensive.
Now here comes the rub, you almost cannot have too fast or too powerful a servo. Please repeat!

I know this comes as expensive news to some, but if you really want a precise model that performs, you need to pull out that Visa and invest in at least #3 for all control surfaces.



I got this info from Dave Patrick