Any way, getting back to the abbreviations, the only difference in the two is whether the copolymer has more than 50% vinyl acetate. If it does, go with the VAE, otherwise stick with the EVA. Strange and rather arbitrary.
I'd love to see someone proposing the similar name change for say, ABS (a terpolymer of acrylonitrile, butadiene and styrene), constantly renaming it depending on the relative amounts of A, B and S. Whoever would suggest such a system would already be starting in a hole since there typically is more styrene in the material than acrylonitrile or butadiene. But think of the possibilities: we could have 6 options:
EPDM (ethylene, propopylene, diene - don't ask about the M) could also face a name change to PEDM (at least the D is consistently in last place).
Anyone proposing such a crazy scheme would probably be tarred-and-feathered (wood tar of course, since we want to biosource it!) so why do we tolerate it for EVA/VAE? Personally, I prefer EVA - it just rolls off the tongue so much better than VAE.