Time Braid is what Chunin Exam Day could have been without a Harem and with a more convincing polyamorous shipping. Its a much better and less drawn out story, for instance there are many other complete AU remakes that go as long and as deeply as HPMOR. However, HPMOR doesn't have the vast amount of fluff and filler that many of the 6/7 multipart fics seem to have(barring SA which I enjoyed greatly).