Draculel,
I think what has happend with this debate which is about 35 years or so old...hmmmm, maybe less--can't remember the exact date that the 63's hit the market--I know I sold them in, I believe 87--and believe they'd been out for some time.
In designing speakers, there's always a moment of OMG, or shock when going from the 2 way to 3 way design...in which you say, well, there's more heft and bass extension on the 3 way, but there's a 'purity' to the voices and midrange that the 3 way can't quite match...I believe that the simplicity, (out on a limb here as I'm only peripherally familiar with the 57's) of the 57 compared to the 63, makes it sound a little 'purer'...and those I trust still claim that to be true when doing that comparison. (That analogy is for comparisons since we're not talking about dynamic two and three way speakers BTW.)
I DO know that the 63 is truly amazing in resolution and purity--the 57 set up correctly must be an amazement to all who hear it. Didn't the BBC use them for monitors 'back in the day', late 50's?
The 'problem' of which is better is an audiophile's 'delicious dream'.
Good listening,
Larry