Swingin' Cat: I think Yanagisawa changed the neck angle on the newest curved sop (SC99X series), but I could be wrong. It wouldn't surprise me to learn that earlier models had unannounced changes in their neck-angles, too. Like most products, design changes may be instituted without fanfare and only when two people compared curved necks would they find out they were different.
I have played a couple of the newest curved Yanagisawa sopranos but honestly don't recall if they were THAT much different from the SC90X series, which I have. The obvious differences are the location of the bell pads and the angle of the bell in relation to the body. By the way, so far I haven't found a curved soprano that plays as good as my SC902, including vintage AND the new Yanagisawas - at least good enough to make me want one.
I know the angles are different among those curved necks shipped with straight sopranos and those shipped with curved sops (and Discreet's photos show those differences very well).
I'm not convinced that the curves make much of a difference. I once had a straight alto and it too made little difference from the audience's perspective. Straight or curved, my altos all sounded like me, just like my sopranos, curved or straight. I think the snake-charmer, oboeish sound that some soprano players achieve comes from their mouthpieces, their tonal concepts, and their embouchure, NOT the shape of their saxophones. DAVE