I think Rubinstein's Beethoven (I heard him in '76 when, as I suppose it was in '75, he couldn't see the keyboard due to the macular degeneration) was wonderful too. But Horowitz' Beethoven? I would question that strongly. What a pianist (I heard him in '75, 2nd row center, immediately behind Wanda), but Beethoven? His interpretations leave me cold.
I had an LP of Horowitz playing Moonlight Sonata. It sent chills up my spine. De gustibus non es disputandum?