No real advantage, per se...the main part of that issue really stems from which synthesis approach you want to work in. Digital sources like the Plaits do "pre-make" the sound in a sense, but you can warp their preprogrammed waveforms all the same.
The real thing I was aiming at in the build above isn't so much a choice between oscillator topologies, but about the point of oscillator doubling. You can have one VCO (of any sort, really) and it'll sound good...but TWO of the same, with the same waveform and a slightly different tuning yields more than the sum of the parts. By using slight detunings, the result is that the sound has more presence...low end stuff hits harder, mids sound bigger, and so on. With the VOID Modular dual VCO, you've got those two VCOs...but the module offers more than just two oscillators inasmuch as you've got the ring mod (probably a 4-quadrant design in there) for amplitude modulation, you can drive one with the other at audio frequencies for FM, etc. However, you can accomplish the same sort of idea with two Plaits and the addition of a ring mod module.
But the big difference is actually in price. The Gravitational Waves is $250; a single Plaits runs $259. So while you could do a dual Plaits setup, just the two oscillators alone are more than DOUBLE the VOID's price. And yes, you definitely need to keep cost-vs-benefit in mind here...