You want our facts and not opinions, but your topic contains some of your opinions. OK then.
I'll do my best to meet your demand.
You're comparing a once $5500 top of the line arranger to a now $1500 middle of the line arranger that actually sits below the SX900. So not really a fair comparison. The T-4 now a Genos and the S970 now a SX-900 is a much fairer comparison. (Facts with some possible opinions)
On the SX-700 clicking one button, the mixer button, brings control of the volume parts using the touch control or wheel to adjust volume parts and more. One button. And if desired live control knobs can be set up to control volume and/or many other parameters. (Fact not an opinion)
I do agree YEM is kinda "clunky" but YEM does the job fairly easy and efficiently once you learn it. YEM is a nice bonus on todays Yamaha Arrangers. (Fact AND an opinion)
The registration does not change because you moved a keyboard. It may "sound" different according to the environment, so maybe have different EQ settings set up on board for those different atmospheres. Again one button, the mixer button / EQ setting (Fact, not an opinion)
That being said, the sliders on the T-4 are nice to have, (opinion) but...
1. The SX-700 has a very responsive modern Touch Screen (Fact, not an opinion)
2. Portability, lighter less bulky (Fact not an opinion)
3. Built in speakers, nice for certain occasions. (Fact with possibly an opinion)
Both are good, but for me it's Touch Screen, Touch Screen, Touch Screen.
Along with the Touch Screen, the choice of physical buttons to access styles, voices, menu, mixers, etc. in combination with the touch screen, quick access home assignable home scree, and control knobs make for a more efficient modern keyboard. (Facts with opinions, sorry it's unavoidable)
Thanks for the topic, but for me if I was still playing out, I would choose the SX-700 over the T-4 and S970. (Oops sorry, that was a complete opinion, and not a fact). Darn forums always with the opinions
I'm just joking around with you Denn. Trying to have some fun.