I haven’t used either, but I find it fascinating that they both share some cool modulation heritage (e.g., wavefolding and dynamics) yet their sound comes across quite different in demos. Taiga has more knocking, thocking, and softer organic sounds in the tunes I’ve heard. The third oscillator adds a lot to the sound too.
In contrast, I haven’t heard nearly as many demos of Cascadia, but the few that I have felt a little more aggressive and dirty, perhaps owing to the FM and ring mod. But the sample size is too small to generalize from.