The Perfect Element cannot be the best song of theirs because of the chorus.
I mean, it's not an unbearable chorus to listen to, but it is a HUGE letdown considering the intensity that they were trying to build through the first verse. The song also doesn't really flow very well.
I find the most emotional Pain of Salvation songs to be the ones with less abstract and more personal lyrics. Such as a Trace of Blood, where you know what Daniel is singing about and you really feel what he was going through there. Or Dedication. That's another one. And Thorn Clown.