Choosing Between PL/PGSQL or C/C++ for Triggers/Store Procs

For a very complex database in which we plan to implement database rules via triggers, I need some information on which language, PL/PGSQL or C/C++ provides the most "bang for the buck" with respect to performance. One initially presumes the C/C+ stored procs/triggers will be faster, but after reading some posts on the list about the Query Planner and PL/PGSQL, I was wondering if using PL/PGSQL might not be better.

1) Is there a clear-cut choice when performance is the issue?
2) Is there a fuzzy choice at work here?  Perhaps PL/PGSQL for simple, obvious stored proces/triggers, but C/C++ for complexity?

Thanks.

-- Clay claycle@cisco.com