We performed the Verdi Requiem in Winchester Cathedral last night. It was a superb concert -- the soloists were great (particularly the bass and the soprano), and the orchestra was good. The big difference in the choir, though, was almost certainly the fact that we sang without scores. This meant that we had few places to look other than the conductor. As a result, we were tighter rhythmically, and much more responsive to the conductor's indications on dynamics.
The choir I sing with, the Southampton Phil, is putting on a performance of Verdi's Requiem next Saturday, in Winchester Cathedral.