"high torque" and "high speed" are really not that important as terms go.

You want to make sure any servo you use has enough torque to do what you want it to do. That's critical.

You get faster and more "locked in" feeling from higher speed servos.

So, when picking servos, pick the highest speed servo you can afford that has the torque you need. (plus a bit of extra torque, just to be safe).

Generally, giant scale sport and scale planes need lots of torque, but they aren't expected to do lots of acrobatics, so slower, high torque servos are fine.

For acrobatics, you usually want faster servos for quicker response. Smaller acrobatic planes, like small 3D planes, really benifit from high speed servos.

Giant scale acrobatic planes need both high speed and high torque, so you get multiple high speed servos ganged together and so on.

Servos also have what is called "deadband", which basically is a measure of how small a stick movement they respond to. If you watch an inexpensive standard servo while very very carefully moving the stick, you can often see where you can move the stick a little and the servo doesn't move. That's the deadband. The narrower the deadband, the more accurate the servo can be.