Geomorph is the most flexible. It can create pretty much any waveform and modulate it in a way which sounds like phasing, PWM, distortion, waveshaping, and sometimes simple filtering - or any combination of the above.
Spectromorph creates filtered sawtooths. It can make pretty much any kind of filter and morph it arbitrarily, but is timbrally limited to the sawtooth even though you have a lot of control of how it gets filtered.
You can use, for example, phase shifting to create squares and pulses but these sound different to normal filtered pulses because the filtering is done BEFORE the waveshaping (which is actually kinda cool, but I digress).
SO what if you had a geomorph wave feeding a filter profile created by spectromorph?! ULTIMATE POWER! Well, maybe
Again, just another oddball idea I've had while fiddling with Zebra, perhaps it would be good for another synth, or a future update. Or maybe it's not plausible *shrug*
