Sometimes it's hard to remember which functionalities belong to which db.
Here are the comparison of all databases as of 4th May 2010.
http://spreadsheets.google.com/pub?key=tAJDpYf8BMl5BHsT2fCIUnA&output=html
Each detail are at
http://1978th.net/tokyotyrant/spex.html
http://1978th.net/tokyocabinet/spex-en.html
NOTE: Some of the functions on tcrdb are accessible as "sub functions" through "misc" method. For more detail, refer to http://tokyocabinetwiki.pbworks.com/37_hidden_features_of_the_misc_method