Which is the better quality Saxophone?

I agree with the other two answers in that Yamaha is a better brand than Jupiter. Their intonation is generally better and they respond much easier than the Jupiter saxes. However you might want to consider some other brands also. My personal preference is for the older Selmer saxophones but the older Conn saxes are also rather good. These saxes are not as popular as they once were so you might be able to pick one up at a comparatively decent price. In addition, buying a used Selmer or Conn would not be too bad of a choice either, as long as its in decent condition. You might consider looking into these. Good luck and happy playing!

The Yamaha 23 is the most popular student sax, and for good reason. Most of the kids in my high school marching band and a few college bands I've seen still use their 23s for marching from 4th or 5th grade and they work fine. You can get a used one in good shape for a really good price, play on it for the first few years of your saxophone journey, and then step up to a pro Yamaha (I love my Custom Z) or Selmer Paris or other pro brand of sax.

Thinking of playing the sax, eh, Jack? :p

If I were you, I would play both (not that I can!) before buying it. Each individual instrument will sound different, and so its possible that in one instance the Jupiter would be better, but in another the Yamaha would be.

If I had to get one, I would get the yamaha. Only because I know it is reliable, and how widely available they are.

The Yamaha is definitely the better sax.