The speed means very little on most of em.
The servos -in actual use move as fast as they can ,considering the load on them -
Consider this:
a servo has a motor and electronics capable of "X" amount of torque.
If we add a high speed gear train - the rated speed will be high (no load speed) but the rated torque will be low.
Now change just the gear ratio.
The rated speed (no load) will be slower but the rated torque will be higher.
Now add the load .This is the real world
The high speed servo may move the loaded surface slowly or not at all
The high torque servo moves the loaded surface faster.
It can be very confusing .
If the modle is tiny and light with small surfaces - you can use the fast rated servo
If the model has larger surfaces which will seea larger air load- go for more torque.
Don't forget, that the speed or torque , is no better than the battery supply to the servo.
a tiny battery trying to dump energy into a big high torque servo may be just as ineffective as a cheap faster rated servo.
keep asking questions - these servo/battery relationships are often ignored and you can spend a lot of money and get bad results.