Seems like these kinds of threads have been overdone here from the looks of the replies, but I'll still put my two cents here.
What I find astounding is how many "metalheads" I know that are big fans of Coldplay. Seriously. What is it with this band? I even had the opportunity to see Coldplay live a couple years ago (Only because the ticket was free, mind you.) I wasn't personally blown away by them. They did put on a solid performance. I'll give them that. What really threw me for a loop was their fans. I saw more asshats at this show than at any metal gig I have ever been to.
Back to the subject at hand, I'd take Porcupine Tree any day. ;-)