i believe that is your only two options if you want the various farms to use
one source. session is on a per process basis as well as all other forms of
cache. if you are farming out on a single machine, state server is better
since the conection is local. for me it's a toss up. i use state server
because of the preciousness of the db. estimates for state server are about
10 - 25% performance degradation compared to session use. i've found this to
be closer to or below the lower end

where the db gains a huge advantage is in the serialization process.
remember for concurrency access, the state store must be locked for each
access. on a heavy site, that can really add up. the same locking occurs at
the database level as well but the database is optimized for high
concurrency usage.

finally, literature doesn't quote figures because it varies so widely.
figures presented can be misleading and completely wrong for unanticipated
scenarios and architectures.