Where does the third fit into the equation?

I browse ruby-talk via the comp.lang.ruby group on Google Groups.
Barring gateway troubles, I think I see posts by everyone on the
mailing list. When I post via comp.lang.ruby, I see my posts being
archived in the ruby-talk archive, appearing in ruby-talk-google, and
being responded to by those I know use the mailing list.

So it looks to me like ruby-talk and comp.lang.ruby are syncing well
(on the whole). Why is there a "ruby-talk-google" group on google,
whose description states:

"This is a mirror list of the offical ruby-talk mailing list. It serves
as a replacement for the old mail<->news gateway (comp.lang.ruby). It
exists to provide access to the mailing list via the convenience of
Google Groups web-based client. (272 members)"

Is it somehow more reliable? Should I be using that instead of
comp.lang.ruby?