How does the UHF link to the orbiter compare functionally to a direct high-gain antenna transmission to Earth?

The UHF link acts as a close proximity conversation, allowing efficient offloading of large files.

The operational difference between using the UHF link locally versus attempting a direct transmission using the rover's high-gain antenna is analogous to the difference between speaking to someone nearby and trying to shout across a continent. A direct transmission via the high-gain antenna over interplanetary distances would result in an incredibly weak signal requiring prohibitive amounts of power. In contrast, the UHF link to a nearby orbiter simulates a close proximity conversation. This proximity allows the rover to efficiently offload megabytes of imagery and scientific data quickly during the brief window when the orbiter is overhead, maximizing the data transfer rate before the line of sight is lost.