Radiohead's not particularly horrible, they're just one of those untalented mass-produced bands that has a vaguely original sound to the casual radio-listener and is relatively inoffensive in the same way the Red Hot Chili Peppers aren't. It's perfectly acceptable to like them, bad bands are just fine. Hell, I'm a Frank Black and the Catholics fan, I think they've got about one song that doesn't basically suck. I'd recommend REM if you want a somewhat pretentious pseudo-novel pop band in your album collection over Radiohead, but whatever, you know?
Coldplay, however, I don't get. It's like someone pretending to be a mosquito. A depressed mosquito. Who plays exactly one chord per song. I've got only a shaky understanding of why people are into music so much, but it seems to me that the purpose of music is pretty emphatically not to numb or annoy, and so Coldplay seems kinda counterproductive. At least the Strokes had that whole I'm-the-drunk-guy-standing-on-the-bar-table-singing-atonally charm for the first time you heard them, and the rest don't get stuck in your head.
