Phil is underrated by Celtics fans, but overrated by everybody else. I think he's pretty clearly a better coach than Doc, but it's not like he will single-handedly lift the Lakers over the Celts.
Also, I agree with nick that Doc has been getting better. He's still not perfect, and his rotations / four-man bench units frustrate me to no end, but if he maintains the level of coaching he showed towards the end of the Cleveland and Detroit series, we should be fine.
The most important thing in this series won't be the coaching, but will be the execution of the players, in particular Ray and Rondo on offense, and everyone on defense.