acquiring | dereferencing an assertion using an artifact

[william <oasis.saml@javafreelancer.net>]

regarding the saml 1.1 web sso browser/artifact profile 
(oasis-sstc-saml-bindings-1.1.pdf),  i am curious to know what is 
the best practice among implementors in this forum in regards to 
acquiring | dereferencing an assertion given an artifact?

possible approaches are:

1. the source site generates the assertion first then creates an 
associated artifact and sends the artifact to an artifact reciever 
service at the destination site; the artifact reciever service 
acquires the previously-created assertion from the source site.

2. the source site generates only an artifact and sends the 
artifact to an artifact reciever service at the destination site; 
the artifact reciever service sends a saml request (containing the 
artifact) to the source site and the source site generates an 
assertion there and then (on the fly); which it sends back to the 
artifact receiver service in a saml response.

my questions are:

a. approach #1 assumes some kind of persistence mechanism 
(in-memory cache, file-system serialization, rdbms, etc...); 
please, can anybody share the pros and cons of this approach and 
the different possible persistence mechanisms?

b. approach #2 strikes me as both the simplest to implement and 
more performant than, say, an rdbms persistence approach; if 
you've used this approach, what are the real-world trade-offs?

many thanks,
will