Git or Hg bridge to SVN

What are reasons to not use a git-svn bridge or an hgsubversion bridge? What are some blatant problems with using a bridge as opposed to fully switching to Git or Mercurial?

I assume the bridge will still be plagued by the slow SVN speeds right?

Thank you.

HGSubversion

• You can't push mergesets to Subversion and must to rebase before push
• You can't use pushable to Subversion Mercurial repo as source for sequential clones: Mercurial rewrites all pushed changesets (thus - change hash) and you'll get copies of full history in each child repo on pull-after-push-to-SVN from parent Mercurial repo, linked to Subversion: bidirectional sync (external Mercurial - Mercurial with hgsubversion - SVN) will not work
• Subversion's merges aren't processed as merges and shown and used as ordinary (single-parent) Mercurial revisions