Verdi's Macbeth opera conducted by Riccardo Muti

I'm sure the UK pressed EMI version probably sounds the best (I have the Carl Neilsen compete symphony set with Herbert Blomstedt and it sounds great).  However I'm only dealing with the two versions previously mentioned. The first set, pressed in 1976 is Angel SCLX 3833 and it is not quadraphonic.  The second set is EMI Angel Voices AVB 34058 and was digitally remastered in 1986. Upon listening to the first few minutes of both recordings, I'm not hearing much of a difference (I'm not usually a fan of digital remastering). However I do understand the earlier Angel pressings are not as good as the later ones. The only other question then is why three discs on the earlier version versus two on the later one. Is there music missing from the later one?  I know there are two different versions of the Opera, but it does not make sense that a re-release of an earlier version would be altered in any fashion in terms of length or quantity.

Runtime seems to be about 2 hours and 7 minutes (as listed for the 1976 version). I can't find any information about the 1986 digitally remastered version (but I would assume it's the same).  There appears to be more music pressed onto side two of the latest version as it goes all the way out to the beginning of act 2 scene 3 as opposed to on the earlier version going out to act 2 scene 1 (how many minutes that is I don't know yet).

I finally got a chance to listen to book recordings and there's very little difference in sonic quality (perhaps the enhanced groove spacing makes up for the DMM).  

There is however, supplemental music on the 1976 version that is absent from the 1986 version.