I am delighted with the SX720, the OS makes it for me, though I'm going to enjoy the extra features as well.
I am loving the new operating system. No doubt a bit of that is the frustration of working with the external screen / buttons on my S900 but even so it's really nice to use. I love all the assignable buttons and I prefer the Registrations/Playlist to the Music Finder, though I'm still getting to grips with it. I find it makes more sense to me than Reg vs MF did (and the QUERTY keyboard is a nice little bonus). The synchro start and audio on the Multi Pads is another plus for me. I haven't played much with the Chord Looper yet, but I will use it once I settle down. I like the new-to-me Chord/Fingering settings also. I prefer the joystick to the wheels on the S900, and that it's assignable is another plus. The Live Control will take some learning, but seems promising. Recording is something I used a lot on my 5700 but not so much on the S900 (I'm not sure why now) so I look forward to using that again. Setting favourites is so easy too. I don't use a Mic so don't know about settings for that, maybe the g'kids will play with it.
Because I'm so enamored with the OS I can't tell if some of the sounds please me more or if I'm just feeling like they do. So far I am not missing any from the S900, but I'm still exploring. No doubt some of them are fantastic, but it'll take some time to know them all, if ever.
I'm a style junkie from old so many of my most used SFF1 styles are missing voices/sounds, but that's easily seen on the screen and quickly sorted. Also, I can now use SFF2... even more styles
Another related bonus is that I can use the Midi to Style program and the styles will work on the 720, my first experiments are encouraging.
As a home player, a hobbyist with a style and midi addiction, if the screen of my S900 hadn't died I'd probably have been more than happy with it forever, but I'd gradually stopped enjoying it. So this is a huge difference for me and I'm glad I took the plunge. Hopefully I can find someone who might enjoy the S900, so I can pass it on.
I'm a happy camper