IME an unstabilized unipivot will always put some limits on imaging and soundstaging compared with a more stable arm design. Channel balance and separation are too easily compromised when stylus azimuth isn't held steady.
That said, a Grado would be my last choice if soundstaging was a priority. That's just not what they're about. The stylus on many Grado models is so huge it's hard to believe it even fits in the groove, never mind tracing delicate HF information.
As others have said, ZYX's are among the champs in this regard, without ever sounding analytical, unmusical or "hifi". IME any ZYX from the Airy 2 up easily out-images and out-soundstages a Koetsu RSP or Shelter 901 for example.
I'd expect good imaging/soundstaging from any cartridge with a modern stylus profile, like the Lyra Helikon mentioned above, Dynavectors, VdH's, ZYX's and others. HF information is crucial for reproducing soundstage, space and "air", and no cartridge can reproduce frequencies too small for its stylus to see.