Finally got a bit of time to write a bit fuller explanation that I promised earlier in the week
When we come to the sound of a Saxophone (In its simplest form) we basically have 2 parts, the articulations and the sound itself, and so to make an accurate Sax sound we need to emulate both accurately.
Due to the way a blown instrument is played and the way a keyboard is played, it is not possible for either instrument to truly accurately emulate the articulations (Operation) of the other, but you can get close.
Sax Sound
This is the basic sound of the Sax itself, and as most keyboards use sampling (Recordings of the real instrument) this can be made to sound excellent, with the limitations being the number of samples that can be stored in the instrument, (The more samples the better) due to the limitations of the available memory in hardware boards they at present cannot compete with software based VSTs etc, but by using clever sampling techniques they certainly do well.
Sax Articulations
Articulations on the other hand are related to how the Sax responds to the players input, and to emulate these you either need a vast amount of samples, (So that when it is played on the keyboard it has suitable samples to play back) or to use sound modelling, where how the instrument reacts is measured and converted into a mathematical formula (Algorithm) which alters the sound in real time (Just like a real player) as you play the keyboard.
The main problems of the sample approach is that you need to use a large amount or memory or disc streaming, where as the sound modelling approach requires fast processing, both of which are currently only generally available in computer based systems, (The main exceptions being the Kurtzweill instruments) and so hardware boards have to take second place.
Yamaha marketing and their R & D however realised that while for true studio production fast computers were needed for accuracy, for the home market (Which is the market arrangers are aimed at) they could simplify this and still give a sound that would impress their intended market, and so SA was born, (For the Pro market this was expanded into EA voices, which give a lot more flexibility and control of the articulations that Workstation uses require, (Or so Yamaha thought, however if you look at a lot of forums the Pros actually prefer the way the home version is implemented) and which uses a much simplified sound modelling technique (Steps rather then continuous variation) and added in just a few more samples to give a more impressive sound.
Coming onto the Korg Sax and Yamaha SA Sax, then the articulations on the Yamaha easily beat the Korg, but the basic sound of the Korg easily beats the Yamaha, and when you compare the 2 with a real Sax (Or a high quality recording) the Korgs basic sound wins out over the Yamahas articulations, thus the Korg Sax sounds more like a real Sax.
Now if you could add the Yamaha articulations to the Korg sound then “WOW” that would be something, however for the time being to me and others, the sound of the Korg Sax sounds more real then the Yamaha SA Sax.
In the end it comes down to personal opinion, and only the individual can decide this.
I hope the above explains better what I was trying to put over in my earlier posts.

Bill