I don’t know your taste in sound design but Syntakt can go far enough, despite being very immediate.
The fact that you got 4 analog tracks and 8 digital with a lot of 'machines" is IMO pretty clever.
Of course there are limitations as in every hardware instrument. You have to set your mind to learn the way it was meant to be used, before coming up with workarounds for the precise things you can’t do immediately.
DNII is certainly deeper, which pushes you to save and load presets to start from more complex starting points, once you’re more advanced.
I advise to listen to the tracks produced in the different SSL to get a good idea of the kind of sounds ST can offer.