Let’s say you wanted a centerpiece synth to your rig. The Op1, while fantastic and glorious for so many reasons, is somewhat lacking in the i/o sync connectivity department. And you want something you can gather your assorted Volcas and pocket operators around. And let’s say you could save $, like almost $200 off the listed price of a Mother 32, which is great, sweet deal, and it is a Moog, and it does have patch points and so much functionality and you know that would be the sensible, responsible adult choice here but DAMN IT that 0-Coast is so sexy and fresh and versatile it is just calling your name, begging you to fold and fold the folded waveforms of crunchy red-panel weirdness into an origami tetrahedron of wet paste and Velcro, patched bright pink and yellow and dedicated to Don Buchla…well what would you do?
Admit myself to the GAS clinic
You can’t give in!
YOU CAN’T GIVE IN!!!
I’d start with one and then buy the others as I could 
I got Mother 32 and almost immediately got a second. Don’t have the 0 Coast, but to me it seems like fun to experiment with, but if you are going for sound, you can’t beat a Moog. Nothing is as rich and delicious sounding.
buchla love? get an O-coast
yes, op-1 is a pain in the ass for running with other stuff but it is a LOT in a little format. Synths, Samplers, Drum Machine, Fun Sequencers and Effects. My only gripe with it was that everything had to be committed to tape so you had to plan songmaking. With a heavy heart I sold mine. Really contemplating getting the OP-Z when it drops as it covers a lot of what I felt the OP-1 lacked - tweakable jamming and sequencing.
Both can be mounted in eurorack too.
My friends and I attended a Moog Music clinic in which a single Mother-32 played melody, bass, and drums using the LFO and filter as extra oscillators. They are big Tangerine Dream fans - the M32 lets you get that sound more easily, because of the onboard sequencer and TD’s reliance on Moog gear during their classic period.
0-coast allows the same extra oscillator trick - no sequencer but it can make sounds the other synth can’t as you noted.
I don’t think either would be a foolish choice.
I think I need both.
But I’m nowhere near considering selling my OP1. I would sooner sell my Honda, a kidney and my everlasting soul before I get my priorities that far out of whack.
I had a Mother 32 and I sold it - recently got an 0-Coast and it suits me so much more.
I have a Moog Slim Phatty and it’s true that the Moog sound is something highly pleasant.
I think I need both.