My thoughts on EQs is you should set it and never touch it again.
You EQ your system so that you get the best response possible from the car & equipment; it has nothing to do with what music you're listening to. Most, if not all, EQs that you'll find in a HU ****. They either sound bad, don't give you the flexibility you need, and I'm not aware of any affordable HU w/an EQ that has different settings for the Left and Right channels.
That last part is key as your car's interior is not symmetrical; so the response will be different on either side.
With that, I'll tweak once and never touch it again unless I change crossover points or the speakers.