I had problems choosing which recording of this opera I should buy. The Abbado studio (French), the Abbado live, the Karajan studio, the Karajan live, the Solti.
There are good arguments for all of them - Carreras and Baltsa in the Karajan studio, Siepi in the Karajan live, Valentini and the two basses (in best shape and roles) in the Abbado studio, Nesterenko and Price in the Abbado live, Solti in the Solti. (The Solti goes away because of the singers, especially Fischer-Dieskau being plain wrong.)
But fate made me end up with the Giulini. Here I have a Domingo in one of his best roles, a Milnes that is ideal (next to Bastianini) as Posa, a Caballe that has one of the most beautiful voices ever, a Verrett that is full of blood. (Actually it's completely amazing to hear Domingo and Milnes together, even their perfectly balanced vibrati are syncronized!)
And some great orchestra playing from the Covent Garden orchestra. And I get Giulini. OK, his tempi are really slow, but the drama he creates! Not a dull moment during five acts.