Allen keys are great. You have a ball end for low torque situations where you need to drive at an angle because of side clearance, and you have the straight end with a slightly longer lever arm for “high” torque applications or to snug up the final 1/4 turn, but not such a long lever arm that people over tighten them and risk damaging the head.
Dedicated ball drivers are more comfortable than allen keys, although I find that even with them, a lot of people manage to apply more torque than is appropriate for the ball head, rather than switching to a straight bit to finish off the job.
Socket hex drivers like this are fine for larger size screws, but the thought of someone using a 12" socket wrench on a 4 mm socket head is kind of scary.
T-handle are the worst since they require clearance on both sides and usually a lot of top clearance. They are good for deeply recessed screws in consumer electronics where an interchangeable bit is too short and a ball driver / allen key can’t safely apply enough torque to break the screw free.
