Drop Colly, after a double century in the only match we nearly held out in plus being the only batsman the Aussies struggled to get out in the second innings of that match. OK so he then went through a lean spell which he came out of with two back to back match winning centuries in the one dayers.

I would rather have more Paul Collingwoods in the England side if it were possible, Englands best fielder, a usefull fill in bowler, a consumate professional and a batsman averaging over 40.
If you want to discount his double century then equally discount his lowest score from the ashes and you come out with an average of approximately 30 which puts him only marginally behind Bell who if you apply the same criteria drops back to 32. And under the same criteria Strauss averaged around the mid 20's and Vaughan just scraped to 20 in his last 5 Ashes Tests.

So even on the "massaged" figures Collingwood is still markedly better than Strauss and a dramatically better than Vaughan. I would conclude that a decision to drop Collingwood in favour of Either Strauss or Vaughan can not be based on cricketing criteria.