I would think 2.4 GHz would be preferable for better WiFi range given the likely low bandwidth needs of the device.
Typically, a device should offer both. 5GHz always being preferred (if the AP is near enough), and 2.4GHz only for when distance is needed.
2.4GHz's long range is also its achilles heel (in addition to its limited channel support). In most any setting, there will be multiple overlapping networks competing for the same 2.4 channel. In a very dense setting (like an apartment building, shopping/strip mall, conference center, etc), 2.4 often becomes completely unusable. Even for low bandwidth devices, the channel contention is so high, devices would be unable to connect.
Now, for a single-family home, this would probably not be a problem. But the V3 seems to target commercial facilities, and those commercial settings are exactly the ones where supporting 5GHz is critical.