What are Relative merits of self-reading and target staff

With self-reading staff, readings can be taken faster than with target staff.
In the case of target staff, the services of trained personnel are essential.
Reading can be more sophisticated with target staff. But if the crewman does not direct the line of sight correctly to bisect the target, it gives a much clearer reading.

The surveyor reads the self-reading staff. But in case of target staff, the staff member is responsible for noting the readings.
It is difficult to adjust the target so that the line of sight divides it correctly.