The '39 Eroica was sourced from NBC lacquers, not the commercial pressings. Cf. the latest Music and Arts Beethoven 9 for the other symphonies in similar sound. 

On the Philadelphia recordings - some of the waxes were played back at the sessions and other waxes were damaged 
in processing. Then came the recording ban ... and by the time it was over, Toscanini had returned to NBC full time and 
Philadelphia had gone to Columbia. Toscanini wanted to redo some sides, but RCA dissuaded him. I think the newest 
transfer is pretty good, considering how much music is at low levels. 

The last Beethoven's were made between 1949 and 1952 .. perhaps the earlier ones were made with the notorious limiter/compressor still in the circuit. The 1952 Pastorale, BTW, contains a huge chunk of the broadcast performance, not the recording session. Same for op. 92. And, regrettably, RCA didn't have the gear that Decca or Mercury had. 

Mike Gray