Generally that widely depends on the emulation, and given the similarities in the hardware, the emulation level shouldn't really be more then a translator, that quickly changes an oculus call that steamvr does not support to the similar steamvr call.Because it's an emulation layer, and it's incredibly rare that an emulation layer would be better than native support.
So yeah, not knowing how it functions it seems an odd thing to say, VR is heavy in terms of system requirements it seems entirely possible that since we are the very early stages that it might just as likely be another issue.