Owen brings up the most important point here: Koha has a community around it, while LK only has LibLime.  Anyone in the world can contribute to Koha, either with patches sent to the patches mailing list [1], with bug reports filed in the Bugzilla database [2], by sharing reports/jqueries/tips/tricks on either the discussion list [3], wiki [4] or newsletter [5], or by participation in IRC discussion [6].  LK has none of those community tools (at least not anywhere where I could find them!).   A statistical work up of the two codebases has been done recently, which is interesting for what it's worth [7].

One can watch Koha's codebase grow daily [8].  LK, like it's predecessor Harley, seems to be a static release rather than a living, growing organism, though I've been told that LibLime does have versions 4.4 and 4.6 in use for their clients (though not released as open source at this time).

As a Koha developer and officer, I'll readily admit my bias, but hopefully the links below, as well as other posts on this thread, can help folks make their own decisions.

Cheers,


-Ian


1. http://lists.koha-community.org/cgi-bin/mailman/listinfo/koha-patches
2. http://bugs.koha-community.org
3. http://lists.katipo.co.nz/mailman/listinfo/koha
4. http://wiki.koha-community.org
5. http://koha-community.org/category/koha-newsletter/
6. http://stats.workbuffer.org/irclog/koha/
7. http://blog.bigballofwax.co.nz/2011/05/24/i-love-pulling-statistics-out-of-git/
8. http://git.koha-community.org/gitweb/?p\x3dkoha.git;a\x3drss