milter or socket?

[Darren Pilgrim]

I'm testing a filter that's available as both a milter and as a 
postfix-style policy daemon listening on a unix socket.  Either way, the 
functionality of the filter is identical.  Which approach is better? 
Milter or unix socket?  In this case, better is actually two separate 
criteria: performance under load and long-term cost of configuration. 
If I slam the server with 5000 requests all at once, which approach will 
chew the load faster?  If I set it up I'd like it to not break over a 
year's worth of keeping postfix current.  I know the policy daemon 
socket interface is pretty stable, but what about the milter interface?