The choice of finger-operated or thumb-operated controller is really a matter of personal preference, with no performance advantage one way or the other.
All controllers have brakes (which puts an electrical short across the motor to make it slow down more quickly, rather than just letting it coast). Parma controllers have been the most popular controller for years
The electrical resistance of the controller is very important as it affects the speed of the car through the corners and the acceleration coming out of the corners. A low resistance gives higher speed in the middle of the corner when applying the power again after braking, and it gives faster acceleration and more "punch" out of the corners. It feels more "instant" and like a switch.
A higher resistance means that the car doesn't accelerate as quickly for the same throttle movement, so it is slightly slower mid-corner and under acceleration.
For the Scalextric home circuit we recommend the 35ohm resistor but it all depends on the track layout and driver preference. For more advanced club racers adjustable hand controllers is the way to go. These controllers usually have adjustment dials to increase/decrease the sensitivity, braking, top speed, antispin and curve. The main advantage is that you can quickly change the controller settings to suit different cars, track lanes or even other track layouts.