Excuse a bout of passion!
I do not wish to do anything either than praise Mr. Prizeman's Libera for what is sets out to accomplish, for it has done so with great success.
But, as one who has sung as a chorister in some of the best parish choirs in America, before becoming a choral scholar at one of the top Oxford college chapel choirs, and a Lay Clerk of the leading cathedral in the Anglican Church, to compare Libera with a functioning parish/collegiate/cathedral choir is like comparing Epcot with the UN: it is a choral style, and not a choral tradition. Ellen is correct. And it IS honest: it claims to be nothing else.
Libera is a choral act/event/group created by the very gifted Robert Prizeman; and a very effective one, but it is not comparable to Leeds Parish/BathAbbey/Romsey Abbey/Christchurch Priory Choirs; all parish choirs that have a full choral commitment bordering on that of a cathedral choir; that are recorded and broadcast as a church choir.
In a previous post I cited the Bob Mitchell Choir, and I would dare to position Libera as the same: a professional choir linked to a parish choir that serves to entertain rather than serve in a church foundation. As an entertainment, Libera is a class act; of that there is no question; but what we see as Libera is not a functioning choir churning out Responses, Psalms, Magnificats and Nunc Dimitti; Anthems and Motets, Masses and Evensongs and Vespers and Complines day in and day out, come wind, rain or no congregation, all for the Glory of God and little pay............which is why I take a little exception at those choirs that do this as being, well, tossed aside as being humdrum compared to Libera.
God Bless Libera, and God Bless the Cathedral and Collegiate and Parish Choirs that carry on day in and day out, with little fanfare, doing their duty, as expected of them.
This following BBC video is forty years old (though it looks fresh enough to be filmed yesterday) and was filmed when I first sang as there as a lay clerk: these faces are now fathers; doctors; famous composers and conductors and ordinary men. I recall one cold January Evensong taken by the Archbishop, at which the choir sang with just two ladies in the congregation; one of these boys asked Archbishop Ramsay: 'Sir, why do we bother, if no one comes?" to which he replied: "We do it because they could not be here". It is a duty, not an 'entertainment'.
http://www.youtube.com/watch?v=aVC3EB7yXlM
To me these boys sing this with as much vigour and commitment and passion as any choir anywhere at any time - and they knew WHY they were there. So please.....let us enjoy Libera, and the others serving in quires and places where they sing, for what they are, and not try to compare them with each other, for they are not comparable.
. I think the ancient traditional choirs have a much more complex and full sound which remains constant over decades and is unique to each choir. If they "performed" directly to their audience like Libera, they would be streets ahead, but that’s not the way of the Anglican church. (which is an issue for a whole different forum). 
