[radiodurans]

Feel free to add other completions in the comments.

 

[vtpoet]

Surprised nobody has taken you up on your poll. I have several versions on CD, then stopped buying version after version when the miracle of Spotify turned up. I picked Süssmayr, though Levin is a close second. The thing about many of the reconstructions is they all get apoplectic when it comes to the Benedictus---and they all ruin it. I studied at the Cincinnati Conservatory of Music, composition, and I do get the compositional/unidiomatic mistakes that Süssmayr makes, but what he got right was the spirit of the requiem. It's a really lovely piece of music. And given that it's the most lovely thing he ever wrote, I'd place pretty good odds on the likelihood that Mozart gave him some guidance (verbally or lost). All attempts to fix the Benedictus, while true to the letter of the law, manage to drain the spirit right out of it. If Süssmayr was no Mozart, modern scholars are no Süssmayr.

Incidentally, there was a completion of Mozart's requiem written by a contemporary living in Spain (I think). It's been recorded and I've forgotten which recording it is.