If CS had already run a mid 27 10k which he easily could have last year, or earlier, 26:59 would be logical. Also, if Ritz did a sub 27 it would have been almost expected. You expect big PRs in the 10k. It is really shocking for a 10k/marathon guy coming down to the 5k and running a career best race, well into his career, that is rare. For a guy with a lot of speed and good training to come up to the 10k, as a mature track runner (but not too old ala Kennedy or Goucher) you expect great results. Alan Webb even showed that as a 1500 guy. I gotta go with 12:56 and say I'm surprised at the poll results. If Dathan ran than 12:56 last weekend by winning a race at Stanford I think the results would be different. They're both great records, of course.