Mercurial      git                     BK (*)
storage             revlog delta   compressed revisions    SCCS weave
storage naming      by filename    by revision hash        by filename
merge               file DAGs      changeset DAG           file DAGs?
consistency         SHA1           SHA1                    CRC
signable?           yes            yes                     no       

retrieve file tip   O(1)           O(1)                    O(revs)
add rev             O(1)           O(1)                    O(revs)
find prev file rev  O(1)           O(changesets)           O(revs)
annotate file       O(revs)        O(changesets)           O(revs)
find file changeset O(1)           O(changesets)           ?

checkout            O(files)       O(files)                O(revs)?
commit              O(changes)     O(changes)              ?
                    6 patches/s    6 patches/s             slow
diff working dir    O(changes)     O(changes)              ?
                    < 1s           < 1s                    ?
tree diff revs      O(changes)     O(changes)              ?
                    < 1s           < 1s                    ?
hardlink clone      O(files)       O(revisions)            O(files)

find remote csets   O(log new)     rsync: O(revisions)     ?
                                   git-http: O(changesets)
pull remote csets   O(patch)       O(modified files)       O(patch)

repo growth         O(patch)       O(revisions)            O(patch)
 kernel history     300M           3.5G?                   250M?
lines of code       2500           6500 (+ cogito)         ??

* I've never used BK so this is just guesses