Mainly I’m interested in sounds I’ve never heard before.
My favorite VSTs are Aalto and Kaivo by Madrona Labs. My favorite hardware is the Gotharman’s Tiny Little Deformer - which also has a touch screen and just four knobs, is the size of my hand, and is a powerhouse.
I’m interested in the Zynthian because it does so very much. Many times I’ve looked at a high end flagship synthesizer/sampler/workstation and thought, “but wait, it doesn’t have a granulator, or physical modeling, or this particular effect I’m interested in…” but Zynthian potentially does.