I've been using BAM since their beta-test, and also a quick test of GridRepublic.
BAM has most options, and most projects to choose from.
I'm mostly using BAM to attach/detach projects, and to join new projects.
For anyone with lots of computers, especially the new features like "attach/detach to project on all computers" could be a help. Also, the delayed detach (wait until all work crunched and reported) is one of the many improvements in resent BOINC-clients.