Monero is testing LMDB
Boolberry is testing LevelDB
What will Aeon use?
Probably LMDB. I had concerns about LMDB not supporting 32 bit but that seems to be getting resolved.
There are some things to like about LevelDB though, and the Bitcoin developers are happy with it. My main criticism is that I've heard it isn't maintained any more, but there are LevelDB forks that are maintained.
LMDB more stable. Monero make right choice