co.uk
If you must choose one, choose .co.uk.
El Reg has (thankfully) never been one to worry about bucking trends. Just because a bzillion other sites wish to bury their distinctiveness in the all-consuming .com TLD, that's no reason for El Reg to do so.
Besides which, who ever heard of a dot-co-dot-uk bust? Ergo, .co.uk is a lot safer from a business standpoint.
Adamant of Tonbridge Wells