electromechanical vs hydraulics

As a rule it is the Process Engineer that determines the usage.

I have used stepper motor drives though rack & pinion to give linear movement accuracy down to 1micron but able to apply force up to 10tonnes.
I have used hydraulic proportional valves in a motion control application to rapidly accelerate to synchronise with 3rd party conveyors; smoothly and without overshoot.
Just 2 examples within past projects - would suggest the pros and cons depend on the application.