In Man of Steel there were various instances of Kryptonians using silver fluid gizmos as part of their technology. Such gizmos were in the scene of birth, in the scene where Jor El is talking with Lora's image inside of a robot, or when Jor El explained Krypton's history to Clark.
But Jor El was imaged by an ideal hologram (on Earth). Then why did they use those silver things when they could make such holograms? Is it flaw of the plot?
The technology being used (on Krypton) is over 18,000 years older than the technology in the shuttle. It's quite reasonable to assume that in that time, fads have come and gone. It may simply be that modern Kryptonians are into metal communicators this season.
One of the key reasons that council inadvertently destroyed Krypton is because they were mining the core of the planet for energy. Assuming that holograms use up more energy than the metal displays, then it makes good sense to use that option rather than having costly holograms all over the place.
In the film, holograms are only used in fixed installations (e.g. where the projector can be mounted to a wall or flat surface) whereas the metal "pin art" communication system is capable of free-floating within a mobile structure. It may be that the holograms need to be connected to the Kryptonian equivalent of mains electricity to work properly.
The 'liquid metal' face of the bots can clearly be used to transmit video but that's not what they're actually intended for. The whole point is that it's the bot's literal face, intended to communicate with the user but presumably in a way that couldn't be mistaken for an actual person.
