Can you show any evidence of this, even anecdotal? I've been around online VR communities for a while, and I don't recall any cases of someone being fine with 120Hz, but being sickened by 90Hz.
60 Hz VR will give me a headache, but that's because 60 Hz is below the flicker threshold. 90 Hz should be above the flicker threshold for just about everyone.
All other things being equal, higher refresh rates are better, but there will always be tradeoffs. However, in the 90 Hz+ range comfort won't be significantly affected by a 33% increase in the refresh rate.