Now if only you as were as qualified to talk about clothing
Bickering aside, In all seriousness the way I see it is Radiohead are the equivelent of books like Animal farm / 1984 / War and Peace (books they've referenced in their works especially hail to the thief and Kid A) they're the high brow interlectual band and like those books are refered to as high brow, intelectual and genius. Coldplay they're more the shy kids who write poetry books about their feelings. Nothing wrong with that at all, except of course in the grand scheme of things Radiohead (being the high brow intelectual band) will always get the most recognition.
Radiohead isn't my favorite band (I need more hair in my rock) but I'll listen to them any day over Coldplay. Radiohead is progressive-ish music made by artists; Coldplay is just AIM signature material for when you're feeling blue.
If the most intellectual/brainy rock groups really got the mot recognition, then Muse would be bigger than Radiohead or Coldplay, and the Mars Volta would be bigger than all of them...but it ain't that way. Coldplay is probably the most popular because their music appeals to a lower common denominator.