[Si Coe]

In theory you want a faster servo. You need a moderate amount of torque but most good servo's have more than enough for a 1/10th scale - this is more a 1/8th problem.
The weight of the servo is more important for balance issues than anything else. The ACE 1015 in my 210 is actually rather heavy, but thats good because other 210 owners use an underservo weight instead.

Whilsts its true you get what you pay for, Gavin and I disagree on the subject of value. You can often get 99% of the performance for 70% of the cost. For some that missing 1% really matters but for most club racers, even the good ones it doesn't. You can spend a lot less and still be competitive and have fun.