There is a weight difference between the Tyros 4 and S950...about 10 lbs I think with cases on each. If I was out gigging twice a day like Gary, I might rethink it...but.
There is so much more control of features on the Tyros, the articulated screen, sounds are wonderful...hard drive that has a great operating system so file mgt is so easy.
I've had a lot of time on the S950, and I also own a Tyros4 with the memory expansion.
Although the Tyros4 does not have the audio drum styles, I honestly don't care, as they are very limited as far as editing goes (same on Tyros5) and the T4's other great attributes, like an excellent feeling keybed (with aftertouch) and, the incredibly responsive/expressive SA2 voices (not on S950) made it a must-have for me.
The Tyros4 (and Tyros5) are for the more serious players who take their keyboard playing earnestly, because the overall control and response are quite a bit better than PSR. The FSX semi-weighted keyboard with
aftertouch is just so damn playable.
However, if I was more of an
entertainer and used SMF's, MP3's and the occasional style with not a lot of right hand work, the S950 (or even S750) would be plenty, especially for the older (and perhaps, busier) gigger who wants to save as much weight as possible, although the difference of 10 lbs never bothered me.
I'm still on the honeymoon with my Tyros4, even after more than two years ownership, and I haven't seen or played anything else that would tempt me away.
Well, maybe a Tyros6....
Ian