Both are great snare drums but I'd give the edge to the Supraphonic. It's because of the sound, it doesn't get any better than a Supra.
British Drum Co snares are no slouches though, they have excellent build quality and style. And they sound great too, but not quite as good as a Supraphonic IMO.
Honestly you can't go wrong with either. If the British Drum Co speaks to you more, get that. If you can play them both side by side, that would be awesome. Pick with your ears, not your eyes!