On thing E.O. does have in common with Fonteyn: apparently Margot wasn't a great exponent of Balanchine and having seen Ms Obratzova's Tchaikovsky pas de deux recently, it appears she isn't either.
Yes, Fonteyn was Ashton's Muse; not Balanchine's. I'm not old enough to have witnessed Fonteyn, but I have seen most of the available film footage. I think her greatest quality was her humanity; that's what strikes me. Her stage presence must have been fantastic IRL. If there's one quality that encapsulates the art of Kondaurova, Novikova, Obratzova, Osmolkina, Tereshkina, Ayupova, Pavlenko et.al, it's their humanity. Everything that they do onstage is real. There's no camouflage and there are no circus tricks or vulgarity .
As far as Obratzova's concerned, "Tchaikovsky Pas De Deux" may be, too uh, "Balanchine" for her artistic temperament. A genuine soubrette-ingenue, Obratzova synthesizes lyricism, dramatic ability, Romanticism, and pure academics. "T Pdd" may be too 'virtuosa,' too 'fast,' and too 'extroverted' for her stage persona. Created for Violette Verdy, and IMO, defined
by Patty McBride when I saw her in the mid 70s, I'd say that "T Pdd" is a good example of those characteristics, and probably not Obratzova's best Balanchine showcase. Here is where wise casting, and effective, authoritative
Balanchine coaching (should) come in. This is what Management is responsible for. Obratzova dances an excellent 4th Movement in "Symphony in C." Given the opportunity, I'd think she'd be wonderful in "Emeralds," (the first variation), and if these were in the Maryinsky's rep, works such as "La Sonnambula," and "Vienna Waltzes." MO.