I own a pair of the S9s. AFAICT from online reviews before I bought mine (a month ago), the differences are: slightly lower sound quality in the S10 (this Woot brand), noticeably longer battery life (mine will conk out about 6-7 hrs through my workday), and possibly better fit.
The manual for the S9s has wrong drawings - sometimes the images are mirror-flipped (right-hand buttons on the left, IRL). No biggie; it takes about 2 seconds to learn which side is REALLY the volume adjustments!.
The fit is small, and the manual makes it worse by claiming these are supposed to fit over your ears. Only an 8yo could do that, IMO. However, if you flip them over, and wear them so the back portion rests below the earbuds (and nothing is reaching over your ears), they fit my (6-7/8 hat size, average man-size) head a teensy bit snug - but comfortable for all-day wear.
They come with an extra pair of large ear inserts, and a pair of small. Do yourself a favor, and put a drop of glue on the edges of the earphones to hold the inserts in place. Mine came off the first day; one was lost before I realized this; they DO NOT stay in place without help.
Sound quality is good. Pairing is OK - paired instantly with my phone; my computer was a multi-day hassle, but that prob wasn't the headphone's fault. If no pairing exists when they turn on, they automatically go into pairing mode - bonus! If they lose connection and go into power-save, the only way to reconnect that I've found is to cycle their power - drawback! (It takes several seconds to do this.)
All in all, this is a great price on decent headphones. Be aware of the drawbacks, and if you have a large head/neck, they probably won't work for you.