I hope you're as tired as I am of all the cock-n-bull about Rimsky that we have to endure every time someone reviews Mussorgsky's opera. It is true that Rimsky turned it into a grand opera - it might even be the best work he ever did! But criticism of him fails the mark consistently. I have heard Shostakovitch's version, which sounds like Shostakovitch, and very little of 19th century opera survives. I have also heard Mussorgsky's own "unadulterated" product, and it feeble as an opera - more like a disjointed string of episodes, some good, some bad, and some disastrously inept. At best, it is suitable for a presentation of highlights. So why criticise Rimsky? Without him, there would be no Boris Godunov in the repertoire! Without him, Mussorgsky would be a cipher or a footnote in musical history!
The point is: the greatness and grandeur of Mussorgsky's conception actually survives in his completion.
So now that I got this off my chest, let's turn to Boris Christoff and his impersonation of Boris, Pimen and Varlaam. I doubt it was a happy choice. He sounds the same in all three roles. Until you get used to it and can follow it without a libretto, you can get confused about who is singing, especially when two of them are on stage at the same time. I actually prefer his earlier impersonation (mono only); but only marginally. His Boris is very impressive on all counts, and the stereo sound compensates for some slight reduction in the voltage of his portrayal. What a voice! What a tremendous range of expression!
The other singers are not up to the same standard. But then their roles are nowhere near as weighty or important. Lear is a seductive Marina; but Osunow sound a bit like an oaf, despite the strength of his tenor. The other outstanding singer is Anton Diakov: I hate Rangoni so much, that Diakov's portrayal must be perfect! The Chorus, especially imported from Bukarest on Christoff's recommendation, sing very well, but not conspicuously better than other choruses.
The orchestra and the conductor do a respectable job. You can't compare them with Karajan and the Vienna Philharmonic. But Karajan did not have Christoff to sing for him. That might be a decisive criterion for the prospective buyer. The sound technology is also dated. When the orchestra played mezzo forte or lower, the sound is beautifully soft and ample. But (at least on my set) the climaxes are a bit raw, especially the bells in the prologue, which are altogether oversaturated and downright unpleasant to endure.
I can live with his set. Indeed I've lived with it for nearly 40 years now, buying it three times (LP, tape and CD). Still, I can't in good conscience overlook its limitations, as mentioned above. Younger audiences may not be as forgiving to them as I have grown to be. Therefore they may be advised to check out reviews of alternatives, before they make up their minds.