Going to mod my Xbox 360. Should I flash it or use a modchip. pros/cons?

Going to mod my 360. Should I flash the dvd drive or install a modchip? Which is easier? whats the pros and cons of each method. is there a difference between them?

By The Way, just to clear this up immediatly:
I DO NOT PLAY ON XBOX LIVE SO THERE'S NO POINT IN WARNING ME ABOUT BEING BANNED FROM IT. IT WON'T BE A PROBLEM!