For me, Szell could be very great. His symphony recordings for Mozart Haffner, Beethoven 3, Tchaikovsky 4 and 5, Kodaly, Prokofiev, Wagner are among my favourites. His Schubert (much prefer Bohm), Brahms, Handel I can do without.
That's interesting. To me, Furtwangler sound sometimes artificial, and sometimes plain, but Szell seems to me much more natural. I don't feel he just follows the score literally at all, and knows how to bring things off cohesively, and expressively in a manner that's not cloying like how much of Bernstein comes across to me. I think it all has to do with a certain temperament of the listener, that certain conductors appeal to.Being sensitive to the nuances and emotional underpinnings of a score is not "hamming it up." To the contrary, Furtwängler described his style as simple honesty, following the natural flow of the music like a brook.
To me, Szell's clarity is distracting and draws attention to itself. It sounds unnatural, like saying "I love you" to someone in a detached monotone. Understanding and conveying the character and tone of a work is just as essential to the job of a conductor as getting the rhythms and dynamics correct.
Imagine someone speaking to you naturally, simply conveying what they have to say. Now imagine the same person over-enunciating every word. You would be distracted, and the emphasis on clarity would distract from the actual content, the message. But that's the difference in philosophy. A conductor like Furtwängler puts himself in the shoes of the composer speaking to the audience. A conductor like Szell reads off in strict dictation like a court reporter. This only approximates the content.