First and foremost, I'm a big proponent of using what works for you, and to hell with what works for anyone else.I am absolutely devoted to having a 31 band graphic EQ in my rig...I view the 1/3 octave EQ as the most overlooked and yet most powerful tone shaping tool you COULD have in your rack. It's the FIRST thing I'll put in my effects loop if I had to start over.
To me, a 1/3-octave graphic EQ is a fantastic learning tool to teach your ears what different frequency bands can do to sound. And it's darned handy to move a slider up and down and ask yourself, "Is this closer to or farther from the tone in my head?" But for my purposes, I can get what I want quicker and more precisely with three (sometimes four) bands of parametric EQ.