Sofware decode is broadly comparable so should be about the same.

Later generations often have more tools, which can lead to bigger die size, but this can also lead to energy gains from those tools depending on content/usage.

See cisco's presentation about adding AV1 to Webex and how it could outperform H264 in this niche due to having specific tools for it.

In Netflix type content the grain emulation for example could make a big difference.