I recently bought this recording. I have been listening to Opus 102 played by Casals and Serkin on an old recording remastered for CD. The sound quality was quite poor and also, sorry to say, the performance was very weak. The two great players are frequently not together with piano chords falling distinctly behind by Casals in a very disconcerting manner.
The Brendel and Brendel set is superb. In the Judas Maccabeus variations you hear several lines of music, Brendel father plays with such care and attention that the inner voices sing - even the most apparently insignificant parts can suddenly add a voice. In the Opus 102 #2 sonata in D, once again, the shaping of each individual part is superb and they make of the final fugue a superbly astringent dance rather than a 'would be' Hammerklavier finale [Brendel pere knowing the Hammerklavier as he does it is clear that he is well placed to differentiate the cello and piano fugue from the great solo fugue].
As to Adrian Brendel, his tone is mellow and warm throughout with no lack of virtuosity when required. He must have a superb instrument to play on and I would love to hear him play the cello in the variations to the Opus 127 quartet with the wonderful high cello voicings. Whatever advantages he has had in the music world from his famous father must not take away from his own talent, I have rarely heard such warmth. That he plays in great sympathy with his father is I suppose unsurprising: their performance of the Adagio from Opus 102 #2 is like one long canticle, the intensity of the melisma [so reminiscent of the piano sonata Opus 101] are very finely played.