"Much better" depends on where you're starting from, and what you want to change.
I often get funny looks when I tell people my tenor of choice is a YTS23 - and it's usually followed by comments such as "Ooh, you should try the XYZ...it's a great horn".
Well, I often have - and yet I still have my 23.
I would say that if someone's a 'so-so' player, the difference between a 'student' model and a pro model is going to be very tempting for them...but an experienced player will often look beyond the immediate "What does this horn give me?" and concentrate equally on "What does this horn not have?".
I'd like a bit more midrange tone out of my 23 - something that many horns have - but not at the expense of the simplicity of the 23, nor its free-blowing characteristics and the extent to which it's possible to 'connect' with this very light, very responsive horn.
I was tempted by a Mauriat 66R - big, fat sound and a very easy blow - but it sulked when you backed off compared to the 23, and wasn't nearly as nimble. If it was a car I'd say it suffered from a bit of turbo lag.
I like the 62, and the Z - but the extra depth of tone comes at the expense of a slight sense of detachment (though I moved from a 21 alto to a 62, which came across as a much livlier horn than its tenor counterpart).
My job gives me the opportunity to spend time with a vast array of horns. On any given weekend I have access to a number of fine, pro-standard horns...and I can enjoy the experience of road-testing them without the expense. Some are very impressive, some are very different - and like any other sax player I'm always looking out for 'the next best thing'. I still haven't found it...at least not for a price that isn't silly money (Inderbinen).
I'm not alone though, I work for any number of pro-standard clients who have settled on horns that aren't top-of-the-range. Lots of pros are using Yani 901s, plenty of pros are very happy with Yamaha 61 and 62 horns...some are still using 32s and 21s...so it isn't always the case that the more you pay, the more you get.
Sometimes less is more - and if you're a fan of Top Gear you'll maybe understand why I reckon the Yamaha 23 series is the Ariel Atom of saxes:
http://www.youtube.com/watch?v=WaWoo82zNUA
Regards,