Basic difference between PLC and Relay Logic Control

PLC	Relay Logic
Easy to implement and expand	complex to expand
Troubleshooting and maintenance is easy	Troubleshooting and maintenance is difficult
Can be reprogrammed easily	Reconfiguration is difficult
Interfacing is possible with computer	No interfacing
Required space is less	More space required due to more no of relays
No limitation to no of i/o	Limitation to no of i/o due to complexity
Special training is required	No special training is required
PLC having additional features like PIDs,Timer,etc	No additional features
Wiring is less	Wiring is more
Maintenance required is very less	More maintenance required