CUTUP and I saw Coldplay a little over 3 yrs ago and they put on a freakin awesome show. Unlike some bands, they actually sound good live and are enjoyably entertaining. I would highly recommend checking them out.
As for Radiohead, wicked band, but I have never been to a show.

If you can't decide because you dig them both, just choose one now and see the other next time they make a stop in your hometown??