BitBucket sucks for pull request reviews. The one thing that Crucible does infinitely better is showing the changes from previous commits, and allows you to quickly switch between them, and to only see the relevant changes. BitBucket assumes that any commit is a full change to the source tree, apparently, and on each commit it shows that all the files are unreviewed. Also, Crucible lets you easily see comments that were made on previous revisions, but BitBucket hides them completely unless you go to the overview for the PR, but then you lose your place in the PR tree.