In short, hardly at all (supposing both horns are in decent condition). Without wishing to be too sarky, it is clearly the player that is professional (or not) rather than the sax. 12 months of lessons (with a good teacher) on a YTS23 would be much better than a professional sax without the lessons. IMO.How does a YTS-23 compare to a truly professional sax? Would a beginner be able to tell the difference?
The YTS-23 is a great horn for a beginner. You don't need a pro horn, worry about that years from now. To me it would be like thinking I had to get the same clubs Tiger Woods uses to learn how to play golf...............
I would compare a well set up 23 with new top of the range horn to reading a paperback or a leather bound first edition. You will still get as much content out of the paperback, but the leather bound edition will feel nicer in the hands and more fitting when you are sitting at your finely carved Louie XV1 writing desk in your private mahogany lined library, wearing your velvet monogrammed slippers. But remember Louie had his head chopped off.
It is years from now - see date of post you quoted