RDF storage engines

Hi all,

I am looking for opensource rdf storage systems. I would like to know your
 opinion about Jena&Joseki(1,2), Sesame(3), Kowari(4) or another
opensource plattforms for storaging RDF. Which are its advantages and
drawbacks? Do you know interesting stuff about this topic? Which RDF
storage engine will you choose for a project? 

I find a report which examines a set of opensource triple store systems
for the Simile Project (5). I read also a SWAD-Europe report about free
software storage systems (6).

All the suggestions are welcome :)

Thanks in advance,

.javi


(1) http://jena.sourceforge.net/
(2) http://www.joseki.org/
(3) http://www.openrdf.org/
(4) http://kowari.org/
(5) http://simile.mit.edu/reports/stores/
(6) http://www.w3.org/2001/sw/Europe/reports/rdf_scalable_storage_report