Hopefully, over the next year or so, antenna size considerations will become much less important.
A meta-material composite antenna would have allowed one small sized dual band antenna to be used in the design. There are even antennas that allow for simultaneous dual band use - one antenna with two radio connections.
I have not seen the dual band version yet, but we use one for a Bluetooth radio. It is not much bigger than a large grain of rice, and gets great range and reception.