Arguments for/against use of forwarders{}?

[Steve Snyder]

What are the relative merits of using or not using the forwarders option?

My nameserver (BIND v9.1, running on Linux) provides name resolution for 
the rest of my LAN.  This server in turn can resolve queries sent to it in 
1 of 2 ways: either by contacting the root name servers or by forwarding 
the query to my ISP's nameservers.  For the long term (i.e. caching) which 
is the better method?  

I am not referring to a "forward first" or "forward only" choice, but to a 
simple config like this:

    options {
       forwarders{ 206.13.28.12; 206.13.31.12; };
    };

My ISP's nameservers are obviously "closer", requiring fewer referrals to 
resolve a given name, but they are not authoritative (except for mail and 
news servers).  

A related question: does the use of "query-source address * port 53" 
impact the above decision?  If so, how?  

Thank you.