I have 5 recordings, 3 of them are period style performances, which I prefer; i.e. smaller size ensembles, with lighter vibrato, quicker tempi. The recordings are more intimate (and, I guess, hence better separation). The ensemble singing from these small professional choirs is utterly superior to the choral society type sound you get from conventional choirs.
My favourite is John Eliot Gardiner's recording with the Monteverdi choir and Sylvia McNair. The choral singing is sublime. A close second is Christopher Hogwood's with the Acadamy of Ancient Music, and (the late) Arleen Auger. This uses boy trebles in the choir. Peter Neumann with the Kolner Kammerchor is also good.