I think you are asking the wrong question. The outcome you are using is CPU utilization, but what you are probably looking for is a codec that has hardware support (which reduces CPU utilization and battery consumption).
See this thread for some details:
In summary, h264 has wide support across more devices than VP8, and some h264 profiles even have hardware support on mobile devices (which addresses your need), whereas hardware support for VP8 is limited and it’s likely to be implemented via a software based CPU heavy solution for encoding/decoding.
PS. Be careful about which profile id you use - some profile ids are supported by some devices but not others. This is very browser and device specific.