loc or speaker level inputs

Hello everybody; when connecting a sub amp to a factory HU; what is best; a LOC or use the speaker level inputs of the amp? Thank you.

As far as sound quality goes, it really makes no difference. From a logical standpoint, I would always go with the LOC. Reason being, if you connect the LOC to the speaker wires behind the radio, there is very little chance of running a screw through it or pinching the wire in the door sill. Also if you upgrade your radio, the RCA cable will already be in place. Running the speaker wires through the vehicle always has a chance of grounding a wire and taking out the output chip of your factory deck. Depending on where you live, this may be impossible to get repaired. Just my .02

Thanks I am an idiot; also is it a difference if I use the rear instead of the front speakers?