We use Crucible for our code reviews and I have been happy with it. We use the Atlassian 'stack' so it integrates well with Jira and Bitbucket, which is nice.

We use Crucible for our code reviews and I have been happy with it. We use the Atlassian 'stack' so it integrates well with Jira and Bitbucket, which is nice. It is nice to have all changes highlighted and the ability to make comments on line levels or file level so that the author, and team, can see what is going on and get good feedback.