why not do both if your thinking domestic?
i would say if your thining about doing something industrial i would say "specialise" as theres many different areas, and there is always experts in these areas like:
instrumentation-calibration of sensors and transducers and setting up of control loops
process control- PLC, scada programming
robot programming, well as it says really
motor control, selection and setting of drives and inverters
hydrolics and pneumatic
panel building (i totally believe this is a trade on its own, as some panels you go in are just shocking)
and of cause mix and matching of them all