Definition
While 'incomparably' is widely used, 'uncomparably' is rare and considered nonstandard. If used, it would aim to convey the same meaning: 'to an extent that is beyond comparison' or 'impossible to compare.' However, it sounds awkward to most native English speakers. Think of it as trying to describe something so unique that comparisons fail. Since it's not commonly used, there are no established nuances. Stick with 'incomparably'.